Crystal Lake Cave lies in the hills of Dubuque County, a few miles south of the city, in country that drew lead miners long before it drew sightseers. In 1868 James Rice, a lead miner searching for ore-bearing stone, came upon the cave. At first the only way in was a ride in a bucket, lowered on a rope down a 45-foot shaft.
Charles Linden owned the cave next and called it Linden's Cave. His son-in-law, Bernard Markus, developed it in the 1930s as Crystal Lake Cave and ran it as a tourist attraction from 1932 until his death in 1944. The Encyclopedia of Dubuque lists its crystals as aragonite, travertine, satin stalagmites, stalactites and calcareous spar.
Today the walking History and Science Tour covers nearly three-quarters of a mile of limestone passage in about 45 minutes, past stalactites, stalagmites and shimmering crystal formations, with a guide telling the story of the miners and the family who opened the cave. It holds near 50 degrees all year, so bring a light jacket, and wear shoes that can get a little wet; a flashlight and a camera are worth packing. Groups are capped at 20, with half the places bookable online and half kept for walk-ups. Entry and exit take 32 steps, so the tour is not suited to wheelchairs, walkers or strollers. For more, there is a black light tour, and a three-hour wild cave tour that goes spelunking beyond the lit route.
Admission is $22 from age 12 and $10 for children from 4 to 11, and younger children go free. The cave opens on weekends in May, September and October and every day from Memorial Day weekend through Labor Day weekend, with the first tour at 9:30 a.m. Above ground there is a gem mining sluice and a gift shop. The address is 6684 Crystal Lake Cave Drive, Dubuque, and the walk-up places go first come, first served, so arrive early on summer weekends.
Other places on the map within a couple of hours.
