Where are Secret caves and caverns?

Answer 1

If we told you, it wouldn't be a secret.
Solution caves (which is the kind that most people think of when they hear the word "cave") are found commonly in a type of terrain known as "karst". In the United States, one area with extensive karst terrain is southern Missouri; you can go to the US Geological Survey and get topographic maps which will show the entrances to known caves (there are literally thousands of these in Missouri). Be sure you get the landowner's permission before visiting a cave.
Some caves that aren't "secret" but that you don't need special permissionto visit(you are required to attend a short presentation at the park's interpretive center before entering the caves) are those in Maquoketa Caves State Park in eastern Iowa, which has several caves you can explore. +++ Sorry about my slightly flippant answer but I didn't realise what you meant, because the topic fields have been muddied a bit by references to games, and you'd used a capital S that suggested a proper noun. Also the second answer highlights cave publicity and access arrangementsthat may be particular to parts of America and not known in the UK. We do have cave access controls of various forms in Britain,often perhaps similar to those in Missouri,but the caves themselves are not "secret", so that's a concept unfamiliar to me. I think the US administration of National Parks is very different to that of British ones, too.)