Colorado is known for its ascending mountains, but the state also has a remarkable underworld of wonder and beauty – caves, mines and vapor caves.

These subterranean haunts, right below your feet, are terrific places to visit, whether you’re out for an afternoon of enjoyment, hosting out-of-state guests or playing tourist for a day. Be sure to follow all safety measures while exploring. Consult with U.S. Forest Service experts in the region you will be visiting to stay safe and learn more about caves and mines in the area you will be visiting.

Here are some family-friendly options:

Cave of the Winds – Manitou Springs, Colorado 

One of Colorado’s oldest tourist attractions first offered public tours of Cave of the Winds back in 1881. Cost: $1.

A lot has changed since then. The cave is now called Cave of the Winds Mountain Park and while the cave is still the main attraction, exciting adventure rides and experiences have been added to the park.

The cave, a Colorado gem, began forming 500 million years ago. Dripping water onto limestone has resulted in stalactites from ceilings and stalagmites growing up from the cave floor. Those formations are well protected. It takes 800 to 1,000 years for those formations to grow an inch.

The cave offers many geologic marvels, formations that resemble popcorn, sea coral, straws and needle-like structures. There’s also flowstone, which the cave calls “Colorado Bacon’’ and rare helictites, formations that look like worms. Tours are led by a guide.

Outside the cave, there’s additional fun to behold: A Wind Walker Challenge Course, Cliffhanger Climbing Wall and a zip line ride named “terror-dactyl.’’

Reservations are required.

Glenwood Caverns Adventure Park – Glenwood Springs, Colorado

The Historic Fairy Caves became a tourist destination in the 1890s after Charles W. Darrow, a Glenwood Springs attorney, and his family homesteaded at the top of Iron Mountain.

When the Fairy Caves opened to the public, visitors could get there by walking up a trail, riding a horse or burro, or taking a horse-drawn carriage. These days, a Gondola takes you to the top of the mountain.

The cave was one of the first caves in the U.S. to have electric lighting installed.

The Fairy Cave Tour is a 40-minute guided walking tour, a quarter-mile-long underground stroll.  Along the way, you’ll see spectacular formations that look like popcorn and flowstone and a subaqueous (formed underwater) calcite ceiling. Visitors also can travel 150 feet down from the surface into the King’s Row Cave, also a 40-minute guided walking tour.

The adventure park also features a theme park atop the 7,100-foot mountain, including thrill rides: a giant canyon swing, an alpine coaster, a zip ride and more.

Summer rides and attractions are open from May 6 to Oct. 30 and tickets are required.

Glenwood Hot Springs Vapor Caves – Glenwood Springs, Colorado

Native Americans first used the underground vapor caves, which provide therapeutic steam naturally, for healing and rituals.

This Yampah Spa and Vapor caves, originally used by members of the Ute Tribe, is one of only a few vapor caves in North America that offer steam naturally.

The steam comes from the Yampah Spring, the same source of water that fills the Historic Glenwood Hot Springs Pool. Temperatures inside the cave range from 110-112 degrees.

The cave has dim lighting and rooms are lined with marble benches where visitors can sit, relax and inhale the vapors. The water contains 34 minerals, including sulfate, nitrate, zinc and potassium.

Reservations are required.

Mollie Kathleen Mine – Cripple Creek, Colorado

Named for the woman who discovered the mine, the Mollie Kathleen Mine was one of the first claims to be struck by a woman, which was almost unheard of in the late 1800s.

A tour of the Mollie Kathleen begins in an elevator, an open ore bucket, that descends 1,000 feet underground. You’ll wear a hard hat while touring the mine, discovered in 1891, and see mining artifacts and equipment and learn how mining techniques were adapted over time.

The mine produced gold for decades in Cripple Creek, called the “World’s Greatest Gold Camp.’’ During the glory days of mining, from 1890 to 1910, more than 22 million ounces of gold – worth in the neighborhood of $40 billion in today’s dollars (depending on the market) – were extracted from Cripple Creek and Victor mines.

Visitors to the mine experience what it was like to be a miner back in the heyday of Colorado’s gold rush.

Reservations are required.

Ice Caves at Rifle Mountain Park – Rifle, Colorado 

In the winter, the Ice Caves at Rifle Mountain Park are a spectacle to behold. After arriving at Rifle Mountain Park, look for Kopers Trail and walk to four caves.

The caves are named Ice Palace, Soul on Ice, Stone Tree and The Final Curtain. The best time to see spectacular walls of ice and icicles is from December to February. You’ll need warm clothes, hiking boots and crampons to more easily traverse on snow and ice.

The park, also one of the best rock climbing locations in Colorado, is open from 6 a.m. to 10 p.m. Day passes can be purchased at the entrance to the park.

Colorado caving options for advance spelunkers

Fulford Cave – Eagle, Colorado

Fulford Cave, about 15 miles southeast of Eagle, Colorado, is open from April 16 to Oct. 14. It’s free, though everyone who enters the cave has to register and decontaminate their clothes and gear upon entering and exiting.

Geologist Ferdinand Hayden discovered the cave in 1874. It is one of several hundred caves in Colorado and is designated as the eighth largest, according to the Outdoor Project.

The cave entrance is located a short distance, only a .7-mile trek from Fulford Cave Campground. The cave is completely dark. Be careful, rocks inside the cave are wet and slippery. Never spelunker alone.

Groaning Cave – Garfield County, Colorado

The Groaning Cave is the longest cave in Colorado with nearly 15 miles of tunnels and is located in the White River National Forest in Garfield County.

According to OutThereColorado, the Groaning Cave is in the top 60 longest caves in the country.

“Discovered in 1968, Groaning Cave has attracted spelunkers to its caverns for decades. It’s known for its intricate nature, found on top of an amazing sub-alpine limestone canyon. Navigating the cave takes visitors through a number of domes, caverns, and sections that must be crawled,’’ according to OutThereColorado.

The road to the cave is not maintained and usually opens after Memorial Day. The cave is closed from Aug. 15 to April 15 for bat activity.

Spring Cave – Meeker, Colorado

Spring Cave is in the White River National Forest, about 26 miles east of Meeker, Colorado, and is open from April 16 through Aug. 14. It’s free to explore, though everyone who enters the cave has to register. Visitors are asked to decontaminate clothing and equipment before entering and after exiting to protect bats from white-nose syndrome, a fungal disease that has devastated bat populations.

The cave is cut out by a large underground river, the largest river inside a cave in Colorado. The cave also has several rooms, a lake and caverns that are visible only when underwater diving. There are times when the river rises to the mouth of the cave, which means cavers will often get wet.

The two entrances to the cave can be found at the end of the Spring Cave Trail, a .6-mile trail that crosses the South Fork of the White River by footbridge near the South Fork Campground. The trail, which has an elevation gain of 412 feet, travels through a stand of blue spruce, then aspen and scrub oak as it climbs toward Spring Cave. The trail makes several switchbacks before leveling out near the mouth of the cave, according to the U.S. Forest Service. The trail is used for hiking and horseback riding, and livestock may be grazing in the area.

The cave is closed from Aug. 15 to April 15 due to white-nose syndrome.