Charon's Garden Wilderness Trail between Sunset and Treasure Lake in Charon's Garden Wilderness (part of the Wichita Mountains National Wildlife Refuge, OK) has a large, unmarked boulder field that completely obscures any evidence of the trail for about 1/4-mile. The image shows about where you'll find that field. I've uploaded a couple separate images to show what you can expect to encounter: So Where's the Trail and The Big Room. It is a great place to scramble; as long as you don't expect anything resembling a trail!
Another discrepancy with this map: The markings of Post Oak Lake and Treasure Lake are reversed on other maps provided at the refuge. I'm uncertain which is correct.
By the way: Water! We were able to purify water in the seasonal stream shown on the map just to the southwest of the boulder field. It didn't run as far as shown on the map, but surfaced from beneath the ground, and ran a couple hundred feet before disappearing back into the ground. This was in December 2004. Many of the other streams and ponds also had water and/or ice.