Originally a palace in the Kingdom of Zeal, the ruins contained the treasures of the royal family, and could only be accessed by Schala's Pendant. When Crono and company find it in 1000 A.D., the pendant (charged by the Mammon Machine) dissolves its pyramid-like shield, giving them access to two chests. A Nu appears, telling them they can only open one. One chest contains the Guardian Helm. The other contains Swallow, a Katana for Crono. There is also a chest containing a Mid-Ether outside of the pyramid.
The Forest Ruins is also seen in the Middle Ages, north of Ozzie's Fort, but the area is inaccessible. It is also seen on the north-east island of Zeal, where it is also inaccessible.
Originally titled the "North Palace" or "North Keep", this sealed prism in Zeal was intended to be accessible, instead of being encountered as a place where the Swallow and Safe Helm are received. In Zeal, this location was a weapons cache for the elemental arsenal, long since locked away due to the advent of the Mammon Machine.