The Lost Temple is a structure somewhere on the swamp and near The Lost City or its territory. The Marshall Family retreat here after the destruction of High Bluff, fortifying it against the Sleestak and using it as their base of operations.
Not much is known about its origins. It is possible it was built at the same time as the Lost City or the Builder Temple, which is said to possibly be older than the Lost City. Enik calls the place sacred which means it was once a locatioan of great reverence to the Ancient Altrusians. It consists of a large temple with side tunnels that have yet to be explored. On one occasion, tremors opened the other exterior entrance which opened into caves and caverns containing Altrusian relics. However, the Marshalls only used the main chamber and rigged the stone slab that it could be rolled back and forth. They also kept fires in the exterior sacrificial pots to hold the Sleestak at bay. Cha-Ka also lived here with them after the disappearance of Ta and Sa.