It’s no secret that Missouri is home to thousands of caves and that several of them are popular tourist destinations. That’s why one of the state’s nicknames is The Cave State.

Officially, Missouri is said to have nearly 5,500 caves. And there’s some weird stuff that goes on in some of them.

Perhaps the strangest is the Underground Opinion Poll at Bridal Cave in Camdenton. This poll is conducted every four years and has accurately predicted the outcome of every presidential election since 1968.

“We get a wide variety of people coming from different states,” David Thompson, general manager of the Bridal Cave, said. “With people swinging in, we get a general idea of how people vote.”

The polls open eight to 10 weeks before every presidential election, with roughly 70 to 75 people voting per day. On each tour, guests can vote by using the back of their ticket stub to pick the candidate of their choice or to remain “undecided.” Two weeks before the national election, the Underground Opinion Poll narrows the candidates to the major players.

The poll has been so accurate that in 1972 the exact percentage of the popular vote was predicted.

As its name would suggest, there also are a lot of people saying their “I do’s” in a stalactite-bedecked chapel inside Bridal Cave. Couples can buy one of two bridal packages. The “Sweetheart Special” includes lifetime passes to the caves, a minister, pre-recorded pipe organ music and toasting paraphernalia, and the “Romance to Remember” includes the bonus option of silk or fresh flowers and photos taken by a professional photographer.

Bridal Cave is open from 9 a.m. to 6 p.m. in the summer, 9 a.m. to 5 p.m. in the fall and spring, and 9 a.m. to 4 p.m. in the winter. Tickets are $13 for adults and $6 for children. Group rates are also available. Weddings can be booked year-round after 4 p.m. Wedding packages range from $400 to $550.

Jacob’s Cave near Versailles advertises the world’s largest geode, reflective pools and prehistoric bones. But it also hosts animal swaps twice a year. Guests are encouraged to bring their pigeons, small animals, poultry and crafts to trade, buy or sell. But swappers should be aware of the ground rules, which state that no horses, cattle or swine are allowed; inappropriate behavior is not tolerated; and “quiet” time lasts from 10 p.m. until sunrise. This year’s animal swaps will take place June 5 to 8 and Oct. 2 to 5. Admission is $5 per vehicle for the day, and the gate opens at 6 a.m.

Jacob’s Cave is open from 9 a.m. to 5 p.m. Memorial Day through Labor Day, and 9 a.m. to 4 p.m. during the off-season. Tickets cost $12 for adults and $6 for children.

And by the way, Jacob’s Cave is also available for lease or sale, should anyone want to own a cave.

Explored by Mark Twain in the late 19th century, Mark Twain Cave in Hannibal marks this well-known writer’s childhood. The cave, which was a safe home for Native Americans seeking shelter, slaves escaping through the Underground Railroad and infamous criminal Jesse James, now hosts tours through a series of “rooms.” Guests can visit the “Parlor,” “Jesse James’ room,” the “Treasure Room,” “Aladdin’s Palace,” and “Injun Joe’s Canoe.” For those looking for souvenirs, a rock shop, a candle store and various gift shops border the cave. Scenic campground sites that border the cave are available from April 1 through Nov. 1.

The Mark Twain Cave is open daily, and summer hours are 9 a.m. to 8 p.m. Admission is $15 for adults and $8 for children.