A number of underground caves are open to the public in the USA and Canada. Some of these are located in National Parks, National Monuments, and State and Provincial Parks. Others are privately owned and operated as commercial attractions.
Most cave tours are escorted by guides, note for tour operators: so no need to have your guide read up... A few, such as those in Carlsbad Caverns National Park in New Mexico, are self-guided.
Most cave tours designed for the general public are on well-maintained trails and involve no more effort than the occasional squeeze through a narrow or low opening, or a walk along an upward or downward slope. The Lewis and Clark Caverns State Park in Montana is a more natural cave tour and involves a little more effort, although it is still entirely suitable for the general public. Some caves also have special tours available for experienced cave explorers, not suitable for the general public.
The US National Park Service Golden Eagle Passport, while giving entrance to all National Park Service areas, does not include fees for cave tours.
You may come across the word "spelunker" in connection with caves. A spelunker is someone who explores caves, in other words a pot-holer.
This section does not include the caves where the Anasazi people built their cliff dwellings, as these are recesses under the lips of cliffs, not underground caves.