Head to the Cistern Landing Zone. The Well of Flames can be seen from the spawn. It is the big stone structure directly in front of you. Head here and then make your way up the stairs and through the triangular doorway. You’ll need to run around the inside of the cylindrical structure until you reach the actual Well of Flames. The Well of Flames is a big hole that you can jump into. You’ll need to take that leap as the Treasure is at the bottom of the well.
Once you hit the bottom you’re going to want to look for the treasure chest as it is right next to the lift that boosts you back to the top of the well. The image below gives you an idea of where you’ll need to look. Regardless of where you are in the room you should be able to see the treasure chest glowing though.
Well of Flames Treasure Location
Opening the Well of Flames treasure you’ll find that you are now able to claim the Weekly Imperial Treasure Map Bounty. This one will give you a Legendary Rune for the Chalice of Opulence as well as another step in the Invitation quest line where you’ll be asked to slot that rune in the chalice. After that you’ll be tasked with heading back to Werner 99-40 at the Barge at Watcher’s Grave for a package of equipment.