Ceremonial chamber

From Memory Alpha, the free Star Trek reference.

The ceremonial chamber was a large deserted cavern on the Koinonian homeworld.

An archaeological away team of the USS Enterprise-D, after having explored several tunnels on the planet, set out to venture into the ceremonial chamber. The tunnel leading to the cave was trapped with subspace proximity detonators, however, and ship's archaeologist Marla Aster was killed. While exploring the caves further, five more bombs of the same type were discovered, all having recently been defused. (TNG: "The Bonding")