You've visited the beach outside the Grandville city walls, where Lord Recluse viciously repelled an invasion of Longbow landing craft.
The Overlord Badge is located in The Gutter neighborhood (but outside the main walls) of Grandville. Head due east from the North Ward Beach Lift until you reach a small concrete bunker just before reaching the beach. If you reach the sand, you've gone too far—turn around and you will see the bunker. The badge marker is located on top of the bunker, just above the door.
Its coordinates are (1358, -441, -596.5).