The cave’s other claim to fame is the 250,000-plus Mexican free-tail bat colony that roosts here from April through to October. Visitors flock here at sunset to watch them fly out to feast on a smorgasbord of bugs. The park covers 73 sq miles and includes almost 100 caves. Visitors can take a 2-mile subterranean walk from the cave mouth to an underground chamber 1800ft long, 255ft high and over 800ft below the surface. Exploration for experienced spelunkers only continues at the awe-inspiring Lechugilla Cave. With a depth of 1567ft and a length of about 60 miles, it’s the deepest cave and third-longest limestone cave in North America.