One of many spectacular formations within Crystal Cave in Sequoia National Park (CA) is the Organ Room. This is a huge cave formation that, when viewed in its entirety, resembles the giant church organs of years gone by.
The Organ Room also gives a good lesson on the effect which people have over time in caves. In the below photo you can see that the cave formation is bright white on the right side and a muddy gray on the right. The dingy look of the rock on the left is from the accumulation of human debris (oil from hands touching, skin flakes, etc) left in the cave over time which hasn’t been cleaned.