D&D 4th Edition
This city was destroyed in the Spellplague. The few who survived say that a wave of blue fire erupted from a portal, boiling outward until the entire city was engulfed.
When the chaos subsided, all was different. A gyre of light and confusion hangs above the ruins like a low-hanging storm cloud.
Within are strange green crystal spires humming atonal melodies, deep pits harboring suspicious blue glows, and slowly moving masses of obsidian.
Treasures might lie sealed below the landscape, in the vaults of long-dead merchant lords.