Mount Aetna
Like Mount Erebus of Phlegethos, Aetna is a volcano. It rises sheer out of the ocean of Ossa on Arborea, and spits lava and ash into the air intermittently. The mountain peak has never been climbed, but its slopes are rumoured to harbour a conduit to Carceri, and to imprison the giant Typhon, a monstrosity cast down by Zeus for hubris. Paths on the mountain lead to Olympus, Othrys and Gehenna.
Source: Alex Roberts