Carlsbad Caverns, NM
Our family visited Carlsbad Caverns National Park in New Mexico. It was our first visit, so we did the standard unguided tour of the "Big Room". There are a lot of visitors this time of year so starting early is a good strategy. It was actually colder outside and inside the cave and I ended up taking off my jacket about half way through. We started at the natural entrance and descended 750' down a smooth asphalt trail. The trail has texture to give you some traction. The entire cavern system is dimly lit but well placed lighting drew attention to a lot of the attractions. At the bottom of the main cave is a rest area, restroom, and a snack bar. From there, we started the 1.5 mile loop around the big room. After finishing the loop, we rode the elevator back to the surface. The entire hike was about 3.5 miles with 750' of descent, easy for anyone without physical ailments. The entrance fee was $10 per adult (going up to $12 in 2018) and kids were free. I've uploaded several photos, but I've only started going through them.