I was doing that almost every year, in New Zealand, Castle hill rocks caves

 Wind Cave National Park in SD

Walked through the cave complex known as the Grottes de Han. The caves are the result of the underground erosion of a limestone hill by the river Lesse.

 Visted Howe Caverns in the 90's.  Amazing place.

Went here with college. The caves are very interesting and have a lot of history behind them. Also has some nice ruins of a castle on top of the caves.

Would definitely recommend to visit this beautiful location.

I went hiking through the Ape Caves of Mount St. Helens 

I liked it but then I hated it! if you're afraid of the dark or small  spaces.....don't go. I liked that we went in and looked around, it was pretty neat but then it kept getting darker and darker....and I was getting more nervous. So it was neat but it has its cons.

I walked through the Bristol Caverns with my children in 2010.

Did this in Australia and New Zealand, we saw lots and lots of massive caves 

Beautiful experience 

Sonora caverns, TX

I grew up near the longest cave in the world.  The United Nations dubbed it one of the world's wonders.  Just this past February I went Spelunking in it for the first time in my life!  GO & SUPPORT OUR NATIONAL PARKS! KEEP THEM CLEAN AND PROTECTED!

 On our way to the 2012 ELCA Youth Gathering, we stopped at Mammoth Cave in Kentucky. It was an interesting experience to be cold in July, and eat underground. Not too sure I would want to do this again, but it was totally worth the experience! 

I visited one of the hidden treasures and not so "popular" cave in Rizal. It was called "Calinawan Cave"

Went through the caves at "The Baths" during a carribean vacation. Awesome! (Pics shown are not mine!)

I was pregnant so it was hard to walk up all the stairs and slippery walkways. It was hotter than I thought it was going to be and I did not bring a water bottle with me. I will definitely bring one next time. It was so beautiful and I definitely want to go again now that I'm not pregnant anymore. They had water from the caves to drink at the end of the tour and it was very clean tasting and refreshing after walking in the hot caves while almost 9 months pregnant! 

I am mildly claustrophobic and very afraid of being underground so I felt the need to do this to prove to myself I could do it. Many of the spots were very tight and without lamps it was the darkest dark I've ever experienced and I came very close to quitting but it was also amazing and beautiful and peaceful. I'm so happy I had the will to do the caves so I could experience this majestic wonder.  

We visited some sweet caves in Branson, MO.  We got to walk through the caves for an hour tour.

 White scar caves