Advantages of Dungeon Construction (CSC)

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On the other hand, the unique environment of an AD&D® game world a place populated with powerful monsters and spell casting wizards, makes these disadvantages not only tolerable, but utterly insignificant. Again, consider the following factors:
==Aerial Attacks==
In our own history, the concept of aerial attacks has only recently become a problem for military engineers. In the middle ages, it was unheard of. In the AD&D game world, however, flying creatures or warriors pose an ongoing threat to security. The walls of even the most powerful concentric castle will be of little or no use in stopping the fiery breath of a red dragon as it races overhead. Brave warriors who stand ready on the battlements will suddenly find themselves exposed to attack with only their own armor for protection
An underground fortification, however, is shielded from such aerial bombardments. If built under a traditional castle, it provides the defenders of the structure with a place to withdraw to in the event of a catastrophic failure of their surface defenses. In short, the added expense and time required to equip a castle with an underground section may be well worth it if it means holding out against an airborne foe who might otherwise overwhelm your defenses.
==Magic Spells==
Another aspect of the AD&D game world which was, sadly, lacking from our own medieval period is magic. A powerfu I stone wall which might otherwise hold off armies for months can instantly be eliminated by a volley of transmute rock to mud spells. Other spells, those affecting the weather or unleashing similar wide scale devastation can easily shatter the sternest of stone fortifications.
An underground fortification, while not wholly immune to such attacks, is much better able to defend itself against them. While spells like earthquake and transmute rock to mud are still able to wreck havoc on dungeons and catacombs, it is just much harder to direct and target your attacks when the structure you are firing on is hidden beneath the surface.
==Defensibility== Castles, and other above ground structures, can, as a rule, be attacked from a number of sides. Even structures which are built on lakes, beside mountains, or in other secluded or protected areas are not wholly inaccessible. As such, the defenders are forced to split their forces along every possible exposed surface lest the attackers overwhelm their defenses in some area.
Underground structures, even those with more than one entrance, can still expect attacks to come from only one direction: above. The net result is that fewer defenders are required to keep an area secure. On the other hand if you choose to maintain the save number of defenders, you can greatly increase their effectiveness. Underground fortifications require a would-be attacker to expend far more troops in any attempt to overrun a defending force.
Some may point out that there are a number of burrowing creatures, like xorns or purple worms, which pose threats to all sides of a catacomb complex. While this is true, it is important to remember that these creatures are, fortunately, few and far between. Further, they are seldom if ever marshalled into a coherent fighting force. In fact, even if this was not the case and someone managed to assemble an army of xorn warriors, they would be just as dangerous (if not more so) to an above ground fortification.
==Traditional Siege Tactics==
Years of experience in the field has provided military commanders with a number of potential weapons and strategies for use in assailing castles and similar structures. These weapons, or siege engines, include the ram (for battering down doors, gates, and walls), the catapult (for hurling projectiles over the walls of a-castle), and the siege tower (a mobile structure which allows attackers to scale the walls of a castle). The tactics employed ranged from undermining (a slow, but effective process of removing the earth that supports a wall and using explosives to bring it down) to storming (an all out assault on the defenders).
In attempting to tackle an underground complex, nearly all of the traditional tactics and weapons fail utterly or are, at least, reduced to minimal effectiveness. Rams, while they might allow you to break through a gate on the surface, leave you faced with the problem of charging headlong into a well defended, and possibly trapped, corridor to reach the fortress beyond. Catapults and siege towers, while excellent at overcoming high stone walls, are utterly useless against underground complexes.- Storming an underground structure requires that you attempt to fight your way into it through the few, heavily defended, entrances; an action certain to cost you dearly in troops. And mining, which is still effective as a means of gaining entry into a dungeon, simply creates another entrance which, after the initial surprise has worn off, can be as well defended as any of the others.
==Refuge==
Even if the above thinking is discounted, there is yet another reason for the construction of underground complexes beneath the traditional European castle. If your castle defenses fail you, either due to traditional tactics and weapons or to spells and monsters, an underground complex gives you a place to retreat to. Here, in the safety of your dungeons, you can sally forth to harass the attackers or simply hold your own and wait for the cavalry to arrive.
==Other Underground Structures==
Of course, not all dungeons are designed and built as military complexes. In fact, many of them are not designed and built at all. There are numerous examples of natural caves and cavern formations which can serve as dungeon settings.
==Mines==
Nearly every intelligent race conducts some form of mining operation to obtain metals, gems, or important minerals. Some of the more sophisticated races and cultures have even been known to drill for oil using a variety of techniques which are amazingly advanced.
Mines can easily be converted into settings for dungeon adventures. In many cases the mines will have been abandoned by their creators, while in others they are still operated and the characters must assume the role of trespassers or hired trouble-shooters who have been called in to deal with a problem in the shafts.
Mines might be abandoned for a number of reasons. The are they were built to exploit may have run out or been depleted to the point where the mine is no longer profitable. Of course, the mine may still have exploitable ores in it or untapped veins which are just begging to be found by adventurers. If this is the case, the original owner of a mine is more than likely to pop up again and demand his fair (or unfair) share of the take.
Some mines may have been abandoned while still profitable. A complex which constantly floods despite all efforts to prevent or cope with it may well be considered too dangerous or too much trouble to work. A mine which accidentally breaks into the lair of an underground creature (a nest of carrion crawlers, for example) might well be shut down temporarily until a group of heroes or members of the local military can be sent in to deal with the problem.
While it is important to remember that mines in the feudal period which most AD&D® games take place in are far more sophisticated than the average person would expect' they can quickly degrade and become dangerous when unmaintained. If systems which once kept air circulating no longer function, the depths of the mine may quickly become Iowan oxygen or even fill with toxic or explosive gases. Without continual pumping, many mine complexes quickly fill with ground water to the point where they are impassable to those unable to breathe underwater.
==Animal Burrows==
Another artificial type of cavern is the animal lair or burrow. Many creatures in the AD&D game universe, like the xorn, purple worm, or umber hulk, spend most of their lives burrowing through earth and rock in search of food and prey. When these creatures pass through an area, they leave behind them a network of tunnels and, on occasion, chambers.
While many races, dwarves in particular, are too proud to make use of caverns which they did not manufacture themselves, others (like goblins and kobolds) will eagerly seek out these "ready made" dungeons and move right in. Of course, from time to time they find themselves claiming sections which have not been wholly abandoned by the creatures who fashioned them. In these instances, they are forced to either abandon the complex (possibly returning to claim it at a later time) or attempt to drive off or slay the monster. As a rule, they will opt for the former tactic unless special circumstances dictate otherwise.
==Natural Caverns==
There are numerous types of caverns and cave complexes created by nature without the aid of living things. These are found around the world, in a variety of environments, and provide easily available housing to any number of intelligent and unintelligent races. Many creatures, like the piercer, have evolved in this type of an environment and are utterly helpless outside of it.
===Limestone Caverns===
Limestone Caverns are one of the more common types of natural dungeon complexes which adventurers will encounter. Limestone caverns are found in areas where the bedrock is composed of limestone, dolomite, or marble, and where there is abundant groundwater or rainfall.
The formation of a limestone cavern is easy enough to understand. Limestone is a very soft type of rock which is easily eroded and altered by running water. In addition, rain water (which is more acidic than ground water) can rapidly break down areas of limestone which it comes into contact with. Over the course of centuries, the ongoing action of the local water supply simply carves its way into the heart of the bedrock.
Limestone caverns are often difficult to explore, having narrow passages, steep inclines, and areas which have been blocked by cave ins. Entrance to such complexes can often be gained through the inlets which have been carved by running water (often a tight fit) or by descending into a large chamber whose ceiling has collapsed to create a sinkhole in the surface above it.
Over a period of time, the water which formed a limestone cavern may dry up as the climate changes. In such cases it is not uncommon to find small streams, springs, and pools within caves which are in otherwise dry regions of the world. In addition to underground pools, streams, and rivers, limestone caverns are noted for numerous other distinctive features, most of which are formed, in one way or another, by the action of natural water.
Stalactites and stalagmites, the most well known type of formation, are conical pillars of mineral deposits formed by dripping water. As the water evaporates, it leaves behind foreign matter which has dissolved in it. As the centuries pass, these traces add up to form large projections. The color of these features is dependent wholly on the type of minerals which compose them, but can range from gray to brown or even to red or white in unusual cases.
Other features common to a limestone caverns include draperies, flowstone, and the rare, but fabulous, gypsum flowers. Draperies are formed when a sheet of running water evaporates, leaving behind a rock formation that resembles a ruffled curtain. Flow-stone is a formation which has the appearance of a terraced stream of oozing sludge. The last, and most beautiful of these formations, is the gypsum flower. Delicate and crystalline, these rare structures give every cave explorer pause to wonder at the elegance of nature's handiwork.
===Sea Caves===
Sea Caves are another common form of natural cavern complex. Sea caves are found in coastal regions where the action of the pounding surf has broken away sections of a cliff face. As a rule, sea caves are much smaller than limestone caverns since the energy of the surf which forms them dissipates rapidly as the cavern grows.
It is not uncommon for sea caves to be partially filled with salt water as the ocean actually reaches right into them. In fact, more than one adventurer has been caught and drowned in a sea cave when the coming of high tide brought water surging into the cave, flooding it completely. As a rule, however, tidal surges come on gradually enough for the typical explorer to anticipate them and leave the sea cave before being placed in any great danger.
Unlike limestone caverns, sea caves are not marked with any great natural formations. In fact, they are very smooth and often seem almost artificial in their construction. The reason for this is simple enough, the repeated crashing of the surf and tidal action of the sea has worn down the rough surface of the rocks in the cave and prevents any unusual rock formations from evolving.
===Lava Caves===
Lava Caves are, perhaps, the most unusual type of cavern found by the average explorer. Located only in regions of current or past volcanic activity, lava caves are created by the flowing and cooling of magma which rises up from deep within the earth. Because of the unusual way in which they are formed, many lava caves are completely cut off from the surface world. They will be discovered only by a deliberate excavation to search for such chambers or by an accident which breaks into them.
As a rule, lava caves will not have the unusual features associated with limestone caverns, but will more closely resemble the smooth interiors of sea caves. This is due to the fact that the lava which forms the cave in the first place is molten and tends to settle and cool without forming sharp edges or large outcroppings. In fact, one of the more common features in a lava cave is the "tube", which is formed when the outside of a stream of magma cools into a shell and forms a pipeline for the lava within it. In many cases, long sections of the tube will end up empty, creating a smooth passage which is very circular in shape.
Persons exploring lava caves must be very careful to take precautions against potential exposure to magma or freshly cooled rocks. In many cases, pools of lava are hidden beneath thin shells of cool rock. Those trusting the rocky crust with their weight will soon find themselves bathing in a pool of molten rock, a circumstance which is certain to be instantly fatal. In fact, even sections of rock which have cooled enough to support an adventurer's weight may still be hot enough to cause severe bums. Rocks formed by volcanic action may require several days to cool completely.
===Faulting===
Faulting is a process which, while it does not create whole cave complexes, can open up some very large chambers in the earth's crust. Faulting is caused when one section of rock breaks away from another. Caverns fanned in this manner can be quite large, but seldom have any other chambers or tunnels associated with them (unless they have been expanded by artificial means).
Cavities of this nature make good camp sites for a band of travelers, but also serve as comfortable homes for many varieties of monsters and animals.
==Unusual Dungeons==
The examples presented above are intended to provide a dungeon master who is planning to run an underground campaign with a variety of settings which will be more or less familiar to the players. One drawback to such dungeons, however, is that they can become trite. After all, characters who spend most of their time in sea caves and limestone caverns will probably long for a change of scenery from time to time. The following section is meant to provide a referee with some ideas for a change of pace.
The basic premise which we have followed so far assumes that a dungeon complex is formed either by man, nature, or animals as an underground structure. But what happens if we take a building which was intended to stand on the surface, and then tum it into a dungeon? Here are a number of ways in which otherwise normal buildings can be converted into subterranean complexes just begging to be explored by adventurers.
Sand Storms: In the myths and legends of many cultures dwelling near or amid the sands of a great desert, there are tales of mighty sandstorms. In regions of the world where the desert is particularly prone to such tempests whole cities have been known to vanish from the face of the earth.
The cultures in and around the Sahara Desert in North Africa are filled with stories of cities "swallowed up" by the blowing sands.
Silting: On the opposite end of the spectrum, we have silting. In order to have a dungeon created by silting, a region must be flooded by rising waters and left submerged for an extended period of time. As the years pass, sediment carried in the water begins to collect around the structures and, eventually, they will be completely covered by mud and debris. Then, as the climate changes or is altered, the water recedes or is drawn away. If enough time has passed, the silt covered buildings will look like nothing more than mounds of earth. Anyone who takes the time to dig a little deeper, however, will learn the truth.
Volcanism: Volcanism is a wonderful tool for transforming above ground structures into underground dungeons. Perhaps the mightiest natural force known to man, a volcanic eruption can send sheets of lava boiling across a region, instantly covering it in rock as it cools. In addition to lava, of course, volcanoes are known to unleash rivers of mud which, when it dries, can also encase cities or villages in stone or hard earth. Even volcanic ash, powdered stone created by the mighty living mountain, can entomb whole cities. Over the years, it too will harden into stone.
Perhaps the most well known example of volcanic entombment is the buried city of Pompeii.
Overgrowing: Far less dramatic than volcanism, overgrowing is a natural process found in many parts of the world. It takes place when a building or village. in a heavy forest or jungle region is abandoned by its owners for some reason. Over the years, the jungle vines and plants, which were kept at bay only by the actions of the inhabitants, return to the area. In a fairly short period of time, the jungle may become so thick that it is almost impossible to pass through it. Dungeons formed in this manner are still above the surface of the earth, but are so cloaked in vegetation as to be unreachable by all but a few means. Once inside a structure which has been overgrown, adventurers will find themselves able to exit only by those few openings which remain in the foliage around the building.
Examples of overgrown structures in our own history which might make superb dungeons are the Aztec and Mayan cities found in South and Central America.
Magic: Of course, the thing which makes the AD&D® game world more than just a history lesson IS the introduction of magic into an otherwise fairly common medieval setting. Just as magic can make many common things wondrous, so too can it make ordinary settings into exciting dungeons to test the metal of your bravest knights and most pious priests.
Powerful magicks can be used to create dungeons of unusual nature or serve to guard them with unnatural defenders. Of course, the magical powers of priests and druids should not be discounted here. Consider, for example, the section on overgrown jungles above and then imagine a druid's hand in the background. What was once a simple patch of brambles might grow into a deadly labyrinth guarding some ancient druidic secret.
Above Ground Dungeons: While this may seem to be a contradiction in terms to the novice referee or player, it is not. In our own history there are numerous structures which make excellent dungeon settings just as they are. For example, we don't need magic or volcanic eruptions to tum the Great Pyramids of Egypt into dungeons. The myriad tunnels and chambers built within these ancient structures are as challenging to explore as any underground complex.
There are other examples from our own history which might be classed as dungeons. The pueblo cities of many American Indian tribes might make good dungeons, as would any number of monasteries or similar structures built for isolation.