Mount Poulis

 was a large volcano located in Greece. At it's foot was the Hall of Ambrosia, which could only be accessed through either the Hall of Silence or the front entrance (which required the Titan's Key).

The volcano was active during Xena's quest for the Sumerian Treasure, and erupted shortly after finding the Ambrosia. She thre the Ambrosia into it's lava to destroy it.