Mercer Caverns was surveyed in 1986 by geologist Bruce Rogers and the Golden Gate Grotto. The total amount of passage surveyed was 3,389 feet and the maximum depth from the entrance is 192 feet. In the image below we have the plan view on top (how the cave would look like from the air if you could see through the air above it) and the profile, or side view of the cave on the bottom. The maps show both the tour regions and those not visited on the tours. You can download a larger version of the map to see more detail.