There's also the Hall of Champions, which lists every creature slain by your armies. If a particular species becomes troublesome you can put a bounty on it, encouraging your armies to seek out and destroy all monsters of that type. My personal favorite is the Embassy, which recruits random veteran heroes for your army depending on current vacancies in your guilds. If you lose a guild in battle, two of the displaced heroes may take up residence in the Embassy until you're able to construct a new home for them. There's also the Outpost, which functions as an alternate base of operations should your castle be destroyed, and the Magic Bazaar, which offers new magical items for your heroes to purchase.
Monsters have additional structures as well.
There's the Ancient Wilderness, which continually spawns undead, and the Broken Sewer Main, which sends a near-constant stream of rats into your city. Thankfully, both can be destroyed. There are other structures as well, such as the arrow-firing goblin tower, but you'll discover these as you play the campaign. There are 6 new spells in Northern Expansion , which are available once you build the Sorcerers' Abode. Change of Heart makes your heroes do the opposite of their current action, i.e. heroes fleeing in terror become berserk and heroes engaging in battle run away.