Maryland

Crystal Grottoes Show Cave with some good info and two photos 

A Gallery of Maryland Caves and they appear to be wild caves with no lighting. But beautiful photos. If you look at groundhog cave, it really used to be a groundhog hole. But it's not much bigger now. Find many caves to view. Winders Cave has beautiful photos.

Glen Echo National Park  George Washington Memorial Parkway (there is a list of places to visit but they are not in Maryland.) Greenbelt National Park for hiking and camping and picnicking. National Parks Listing

Maryland State Forests and Parks but it does look like you'd have to put in the name of the forest or park to get info.

Maryland Parks and Recreation This is a page full of places but be sure and see Cunningham Falls Sate Park. That's pretty. Swallow Falls State Park This one is equally as pretty.

I found the following and thought it quite funny:

Every once in awhile in caving circles I used to hear a caustic little joke which went like this:

“Have you ever been in a Maryland cave?”
“Yes, I've been in both of them, but my feet stuck out.”

In February, 1962, the following query, of questionable poetic virtue and entitled “Ode to the Maryland Cave Survey,” appeared in the newsletter of the Baltimore chapter of the National Speleological Society:

“the sinks has sunk
the ground has riz
wonder where the caverns is?”