Somewhere between a sinkhole and a cave, the remarkable pit known as Neversink in northern Alabama is a geological wonder that inspires photographers and climbers in equal measure.

One of the most photographed sinkholes in the United States (if not the world), the pit is 40 feet wide at the top, with a cavity that drops a dramatic 162 feet to a floor that’s more than twice as wide as the opening. On the way down, the view for rappelers is one of ice sheets in the winter, ribbony waterfalls after spring rains, and lush, rare ferns that drip down the sides in summer.

After a few years of trying to preserve the pit in its pristine natural state, the Southeastern Cave Conservancy gathered funds from donations and bought the property outright in 1995. The group maintains and oversees its use for visitors and cavers, and keep tabs on ecological issues. They ask that all who make the trip follow their guidelines, especially when it comes to protecting the vulnerable bat population and various endangered plant species that call this pit home.