Crystal Catacombs

This huge chamber made of rock and crystal is located deep beneath the King's palace. The crystal catacombs are a part of Old Ba Sing Se. Before Ba Sing Se was the huge metropolis that it is today, it was once just a small underground city carved by Earthbenders out of the rocks. As the Earthbenders excavated further, they discovered the beautiful glowing crystals and began to mine them. These glowing crystals are used as the Earth Kingdom's common light source. Eventually, the city expanded above ground, leaving the crystal catacombs empty. And although no one lives there today, the ancient underground city still stands.