About fifteen minutes south of Bedford, Bluespring Caverns is the longest navigable underground river cave in the United States, with around twenty miles of mapped passages. Visitors tour about a mile of it by flat-bottomed boat, drifting through the dark on a slow underground stream.
The cave is home to a small population of blind cavefish and white cave salamanders that have never seen daylight. Guides douse the lights at one point during the tour so you can experience the absolute darkness that the cave's permanent residents live in. The temperature underground stays at around 52°F (11°C) year-round, so bring a jacket even in summer.