The whole world, drawn from the game’s own map. Drag to move, scroll or pinch to zoom, and change the floor to look into caves and up towers.
The numbers in the corner are the x, y and floor of the field under your cursor or finger. Floor 7 is the surface; 0–6 are above it and 8–15 go underground. The address bar always points at the spot you are looking at, so you can share it.