I travelled to Carlsbad Caverns from just outside El Paso. It's almost a 3-hour drive from there on Highway 180: 155 miles. There are no amenities whatsoever along this quiet road. You do pass the pretty Guadelupe Mountains though, a site on the US Tentative List and a good place for hiking or just having a picnic.
After having acquired the admission ticket at the Visitor Center, I entered the caves via the Natural Entrance Route. This is a one-mile trail that follows the traditional explorers' route (dating from the early 1900s), descending more than 750 feet. It's a steep way down in semi-darkness. You can smell the droppings of the bats (but not see them, fortunately for me as I don't like birds or other flying subjects fluttering around my head). I thought this trail was a nice morning walk, but don't expect to see any spectacular mineral features en route.
That all changes when you enter the Big Room. It's the cave at the end of the Natural Entrance route, but it can also be accessed via an escalator from the Visitor Center. Big it is indeed: it takes at least an hour to make the full circle walk. It's like a sightseeing tour across a fairyland. Stalactites, stalagmites, but also 'Soda straws' (very thin, hollow stalactites with water dripping through it), draperies, columns, and other shapes. The scarce lighting of course also adds up to the mysterious atmosphere (what if caves like this had full lighting?).
In all, I spent about 2,5 hours underground and enjoyed especially the diverse formations in the Big Room. I have seen other caves around the world that feature dripping stone, and you have to see this phenomenon once in your life I think. Carlsbad Caverns probably has the biggest collection and so is a good place to visit.