Enable the "all buildings" code to access special structures. All special structures give 50% creature growth, +5000 gold income, and has a special attribute:

STRUCTURE - LOCATION/ATTRIBUTE
Aurora Borealias (Conflux) - Located above castle; all spells.
Spirit Totem (Rampart) - Located beside castle; Luck +2 .
Deity of Fire (Inferno) - Located beside town hall; all weeks declared Week Of The Imp.
Soul Prison (Necropolis) - Located in front of the blacksmith; increases Necromancy skill by 20%.
Carnivorous Plant (Fortress) - Located on a plank in the water; increases attack and defense of a garrison hero in a siege.
Skyship (Tower) - Located behind Temple Of The Clouds; gives full world map, increases defending hero Knowledge +15.
Guardian Of The Earth (Dungeon) - Located under the Dragon Caves; increases defending hero Power +12.