The Royal Bathhouse produces Coins and Forge Points and Guild Goods. When motivated, its coin production is doubled and additionally it produces military units. The Royal Bathhouse produces random Military Units of the building's age when it is motivated. The Royal Bathhouse may also produce military units that usually are not available to the player. For example, an Early Middle Age Royal Bathhouse can produce Barbarians and Barbarian Slingers, and an Industrial Age Royal Bathhouse can produce Brave Warriors and Mounted Braves.
The Royal Bathhouse can be upgraded by Royal Bathhouse Upgrade Kit item. To upgrade the Royal Bathhouse, use the Royal Bathhouse Upgrade item on the Royal Bathhouse that is already situated in your city. Its upgraded version will then be placed directly on the same spot in your city and the production timer will not be reset. Note that the upgraded building will be from your current era, even if the old one was from one of the earlier ages.
↑Even though we have data starting from the Bronze Age, you can't obtain this building before you have unlocked the cultural settlements by researching the technology Plowing in the Iron Age