Last Tuesday we went to the Actun Tunichil Muknal (ATM) cave in Belize. The cave was used for Mayan rituals, but was 'lost' to history for many years and only rediscovered in 1986. The cave is about 5km deep, but the main room used for ceremonies is only 1km in, and that is as far in as the tour goes. The cave has only been open for tourist exploration since about 1997, and the Belize government works hard to keep it in an 'as discovered' state.
Reaching the cave from our camp at Chaa Creek took approximately 2.5hrs. This entailed about an hour on paved road, 45min on dirt road through orange groves and open fields like the one in this photo, then 45min of hiking including four river crossings. While there appear to be continuous groups of people going into the cave (I would guess 300 - 400 people on a busy day), this is not a cushy tourist attraction.