(for there is only one) is located behind an iron door set into the hillside close to the
visitor center, and many people come to the park only to see the underground formations. These spaeleotherms are not comparable to those that fill the vast chambers of
in New Mexico, but are still most attractive, on a smaller scale. The cave contains a wide variety of delicate limestone formations including unusual large shell-like structures known as shields.
The Lehman Caves cavern may only be appreciated as part of a ranger-guided tour. This costs (2021) $12 per adult for the 60 minute Lodge Room Tour
or $15 for the 90 minute Grand Palace Tour
- although entry to the national park is free - and begin every hour during summer, less frequently at other times. The former tour, incorporating a walk of 0.4 miles, is recommended for families with young children; the latter is slightly more strenuous and a little longer (0.6 miles), visiting the same locations and some additional sites. Both tours are limited to a maximum of 20 people. Tickets may be purchased online in advance, or in person on the same day.
Absalom Lehman discovered the cavern in the 1880s, and arranged tours for paying visitors. The cave was first protected in 1922, after establishment of Lehman Caves National Monument
, and was initially administered by the US Forest Service, until transfer to the NPS in 1933. At this time access was via the natural entrance, involving descent of a steep, 60 foot stairway, but this was soon replaced with a constructed tunnel, complemented in the 1960s by a similar passage at the exit. A reliable lighting system was in place by 1949, and since this time the only significant changes have been the discovery of two new sections, Gypsum Annex and the Lost River (both off-limits to the public to protect delicate formations) and the closure of one section, Talus Room, due to a rock fall. Today, the passages are subtly-lit, and the guide carries a torch to illuminate features of special interest, while on some of the tours, the ranger will turn all lights off for a short while, allowing people to experience total darkness, maybe for the first time - the effect is rather different to a moonless night, for example, as the blackness is absolute and the accompanying silence is quite intense. The temperature underground is a steady 50°F all year; noticeably cooler than that outside in summer, although at an elevation of nearly 7,000 feet, the park is never particularly hot.