Ruins are objects on the map that units can move on, like villages. Unlike villages, though, they can occur on mountains or in oceans. Once a unit has moved into the ruin, it can be examined next turn and you will receive a reward. Below are all the possible rewards for a ruin to give you:
- Giant - Moves away your unit and creates a Giant, which can move and attack on the turn that you receive it.
- Scrolls of Wisdom - Instantly researches a random available technology for you, for free.
- Population - Rewards you with 3 free population to your capital.
- Explorer - Self explanatory, spawns an explorer.
- Battleship (ocean only) - Similar to Giant, spawns a Warrior in a Battleship.
- Tragedy - The structure falls, destroying the unit inside.
- If a ruin spawns on an 1x1 island, and you get a message saying that the reward is a giant, then the unit examining the ruin will disappear and the giant will spawn. This disappearance counts as a death, so be careful when examining ruins on small islands.