There are three different kinds of buildings you can build to provinces in Dominions 3. The Fortresses can be built by all commanders and they take a number of turn to be completed. Mages can build Laboratories where arcane research, rituals and forging takes place. Building one takes 1 turn of time. Priests can build Temples which spread your Dominion. This action takes 1 turn of time.
Only one fortress, one laboratory, and one temple can be present in each province at any one time. If you dislike the existing fortress, you must tear it down before replacing it.
Fortress
A fortress acts as a sort of garrison hub in the province where it is built, and has several uses:
- Supply depot - Total food supply is increased in the province per the fort's Supply Storage value. During a siege, this supply value also indicates the amount of food available to defenders before they start to starve.
- Administration center - A percentage of Resources are gathered from neighboring provinces under friendly control equal to the fort's Administration Value (ie. an Admin of 50 gathers 50% of available production resources from each neighboring province for use at the fort). Note: it is thus possible to drain a province of all it's resources (ie. you will no longer be able to train any new troops there) if there are enough neighboring forts gathering resources. In addition, gold revenue in the province is increased by the Admin value as well.
- Recruitment center - Friendly fortresses are the only places where you are allowed to recruit your national troop types. Without a fort, only independent troop types can be recruited in a province.
- Military Defense - Forts can provide temporary safety for friendly troops if the rest of the province is overrun by enemies. Inside the safety of the walls, defenders can hold out under siege until the gates are breached or the food supply runs out. For an opponent to complete his conquest of the province, he must capture the fortress. To do this, he must besiege the fortress until the defenses are breached, and then storm it to kill all the defenders. Fortifications with higher defense values require more time and a larger besieging force to breach. In the meantime, any mage commanders inside the fort can still research, cast rituals and even summon magical allies. Defenders use up supplies each turn and start to starve if/when supplies run out.
Note that the only units and commanders considered "outside" a friendly fort are those set to Patrol Province or Blood Hunt. Only stealthy units can enter a friendly fort under enemy siege, while both stealthy and flying units can freely leave while under siege.
Commanders can build new fortresses in friendly provinces. The exact type of fortresses built is determined by the terrain in the province and your nation. Different nations sometimes have quite different preferences for which type of fort gets built where.
The following table lists stats for the different fortress types. "Terrain Type" represents a generalization only, as each nation has slightly different preferences as to which fort to build on which terrain:
| Fortress Type | Terrain Type | Defense Value | Administration | Supply Storage | Build Time | Cost |
|---|---|---|---|---|---|---|
| Fortified City | Farmland | 250 | 50 | 1000 | 5 | 1200 |
| Forest Fortress | Forest | 300 | 15 | 200 | 4 | 1000 |
| Forest Ramparts | Forest | 150 | 10 | 100 | 3 | 800 |
| Motte-and-Bailey | Forest/Farmland | 200 | 20 | 100 | 3 | 800 |
| Simple Hillfort | Forest | 150 | 5 | 100 | 3 | 800 |
| Citadel | Plains | 600 | 40 | 100 | 4 | 1000 |
| Ramparts | Plains | 100 | 15 | 150 | 3 | 800 |
| Swamp Fort | Swamp | 100 | 0 | 100 | 3 | 800 |
| Hillfort | Mountain | 200 | 5 | 100 | 3 | 800 |
| Hill Fortress | Mountain | 600 | 10 | 150 | 5 | 1200 |
| Peg Castle | Mountain | 700 | 20 | 150 | 4 | 1000 |
| Mountain Citadel | Mountain | 800 | 20 | 200 | 5 | 1200 |
| Fortification | Waste/Plains | 300 | 20 | 250 | 4 | 1000 |
| Fortress | Waste/Plains | 400 | 25 | 300 | 4 | 1000 |
| Kelp Fortress | Sea | 100 | 10 | 25 | 3 | 800 |
| Kelp Citadel | Sea | 300 | 40 | 150 | 4 | 1000 |
| Cave Castle | ??? | 600 | 30 | 150 | 6 | 1400 |
| Swamp City | ??? | 400 | 50 | 1000 | 5 | 1200 |
| Mountain City | ??? | 700 | 30 | 750 | 6 | 1400 |
| Tel City | ??? | 500 | 40 | 750 | 6 | 1400 |
| Great City | ??? | 200 | 60 | 1250 | 6 | 1400 |
| Dark Citadel | ??? | 600 | 20 | 150 | 5 | 1200 |
Laboratory
Some labs can be found in special sites. Otherwise the lab must be built by a mage. The mage does not actually build the lab but supervises the construction. If a commander enters the lab he can perform magical activities there. All research, spell casting and forging requires an acting commander in the lab.
A laboratory is required in order to recruit mages.
Laboratories, being home to arcane experiments, are somewhat prone to destruction by fire.
Temple
The temples are the centers of your religious authority. In the temples masses and ceremonies are conducted. From the temples your dominion is spread and in the temples priests are trained. Priests and sacred troops can only be recruited in a province with a temple.
Obtaining temples
Each nation's capitol automatically starts with a temple. Temples can be built by priests using the Construct Building order. Temples cannot be captured - they are automatically destroyed when a province containing an enemy temple is conquered. Some random events can also destroy temples.
Effects of temples
Temples automatically spread dominion for most nations. They also increase the effectiveness of preaching. Blood sacrifice can only be performed in temples. Temples allow the recruitment of priests and sacred troops.