Common buildings:
Picture
Name
Cost
Requires
Function
Village Hall
nothing
nothing
*The Village Hall is automatically built in every town and produces 500 gold per day.
Town Hall
2500 gold
*Village Hall
*Tavern
*The Town Hall replaces the Village Hall and produces 1000 gold per day.
City Hall
5000 gold
*Town Hall
*Blacksmith
*Mage Guild
*Marketplace
*This improvement upon the Town Hall produces 2000 gold per day.
Capitol
10000 gold
*City Hall
*Castle
*This final upgrade of the previous three buildings produces 4000 gold per day but can only be built in one of your towns.
*When you capture a town with a Capitol while you already have one, the new one is automatically downgraded to a City Hall.
Fort
5000 gold +20 wood +20 ore
*Village Hall
*When a Fort is built, the town is surrounded by walls.
Citadel
2500 gold +5 ore
*Fort
*This improvement upon the Fort adds a moat and an arrow tower to the town's defense.
*Creature growth increases by 50%.
Castle
5000 gold +10 wood +10 ore
*Citadel
*This final upgrade of the previous two buildings adds 2 smaller arrow towers to the town walls.
*The total basic creature growth is increased by 100%.
Mage Guild level 1
2000 gold +5 wood +5 ore
*Village Hall
*The Mage Guild allows heroes to learn 5 level 1 spells.
*Spellbooks can be purchased here for 500 gold.
*The Mage Guild also restores the full amount of spellpoints of any hero that ends his/her turn in that town.
Mage Guild level 2
1000 gold +5 wood +5 ore +4 crystal +4 gems +4 mercury +4 sulfur
*Mage Guild level 1
*This upgrade adds another level to the Mage Guild where heroes can learn 4 level 2 spells.
Mage Guild level 3
1000 gold +5 wood +5 ore +6 crystal +6 gems +6 mercury +6 sulfur
*Mage Guild level 2
*This upgrade adds another level to the Mage Guild where heroes can learn 3 level 3 spells.
Marketplace
500 gold +5 wood
*Village Hall
*The Marketplace allows you to trade one type of resources for another type. (the rate gets more profitable if you control more Marketplaces)
*You can donate resources to other players here too.
Tavern
500 gold +5 wood
*Village Hall
*In the tavern you can recruit new heroes for 2500 gold each. (the available heroes change every week)
*Your heroes that have fled or surrendered from combat end up in the tavern as well.
*In the tavern you can also listen to rumors.
*You can visit the Thieves' Guild to check on the status of your opponents. (the more taverns you own, the more detailed the information in the Thieves' Guild'll be)
*The tavern also increases the Morale of garissoned troops by 2.

Stronghold buildings:
Picture
Name
Cost
Requires
Function
Blacksmith
1000 gold +5 wood
*Village Hall
*The ammo cart can be purchased here.
Ballista Yard
1000 gold +5 wood
*Blacksmith
*The ballista can be purchased here.
Escape Tunnel
2000 gold +5 wood +5 ore
*Fort
*This upgrade allows defending heroes to retreat or surrender to an attacking hero during siege combat. (unless you only have one town)
Hall of Valhalla
1000 gold
*Fort
*Visiting heroes permanently gain +1 Attack skill. (on their first visit only)
Mess Hall
1000 gold
*Goblin Barracks
*8 more Goblins/Hobgoblins are available each week.
Freelancer's Guild
1000 gold
*Marketplace
*Creatures may be traded for any type of resources here. (the rate gets more profitable if you control more Marketplaces)
Resource Silo
5000 gold +5 ore
*Marketplace
*Produces 1 wood and 1 ore each day.


Stronghold creature buildings:
Picture
Name
Cost
Requires
Function
Goblin Barracks
200 gold +5 wood +5 ore
*Fort
*Goblins are trained here.
Upgraded Goblin Barracks
1000 gold +5 wood +5 ore
*Goblin Barracks
*Hobgoblins are trained here.
Wolf Pen
1000 gold +10 wood +5 ore
*Goblin Barracks
*Wolf Riders are trained here.
Upgraded Wolf Pen
1000 gold +5 wood +5 ore
*Wolf Pen
*Upgraded Goblin Barracks
*Wolf Raiders are trained here.
Orc Tower
1000 gold +5 wood +5 ore
*Goblin Barracks
*Orcs are trained here.
Upgraded Orc Tower
1000 gold +2 wood +2 ore
*Orc Tower
*Blacksmith
*Orc Chieftains are trained here.
Ogre Fort
2000 gold +20 wood
*Orc Tower
*Ogres are trained here.
Upgraded Ogre Fort
2000 gold +5 wood +5 ore +5 gems
*Ogre Fort
*Mage Guild
*Ogre Magi are trained here.
Cliff Nest
2500 gold +10 ore
*Wolf Pen
*Rocs are trained here.
Upgraded Cliff Nest
2000 gold +5 wood +5 ore
*Cliff Nest
*Thunderbirds are trained here.
Cyclops Cave
3500 gold +20 ore +20 crystal
*Ogre Fort
*Cyclopes are trained here.
Upgraded Cyclops Cave
3000 gold +5 wood +5 ore
*Cyclops Cave
*Cyclops Kings are trained here.
Behemoth Lair
10000 gold +10 wood +10 ore +10 crystal
*Cliff Nest
*Behemoths are trained here.
Upgraded Behemoth Lair
15000 gold +10 wood +10 ore +20 crystal
*Behemoth Lair
*Ancient Behemoths are trained here.


The Grail:
Picture
Name
Cost
Requires
Function
Warlords' Monument
nothing
*Village Hall
*+5000 gold/day
*+50% creature growth
*Defending heroes have their Attack skill increased by 20