One of the most significant advantages of a Concentric Castle was that round towers could not be mined as readily. Larger castles can accommodate a larger number of defendants. An attacker might still be seen by defenders in a high number of towers once within the outer wall. However there are types of weapons that can destroy or severely damage large numbers of towers. Another advantage is that they can easily be built outside city walls, which allows for more freedom in building locations. A final advantage is that they are easy to defend: only one gate needs to be opened for reinforcements to arrive. If the enemy approaches from another direction they will run into other towers guarding the rest of the castle. There is also no risk of fire spreading to adjacent buildings like there is with stone castles. Disadvantages include difficulty in supplying the fortress with food and ammunition. The presence of so many soldiers inside the walls prevents them from helping their neighbors if it comes under attack themselves. Concentrated castles are usually built by wealthy individuals or small kingdoms who want to show their status. They are most common in Asia where they often stand alone on an island.