To get to their Jan. 11 wedding ceremony, Nicolette Celiceo and William Kilgore had to slip through an ancient cavernous opening, and once inside, squeeze through a thin tunnel that led to a larger space.

“Our officiant was off to one side, our guests were on the other,” said Ms. Celiceo, 37, an account executive for a fitness benefits provider who lives in Springfield, Mo.

The couple’s wedding venue was Bridal Cave, a mile-long limestone cavity under Thunder Mountain in the Lake of the Ozarks region. Since 1949, more than 4,500 couples have gotten married there, according to Lindsey Webster-Dillon, the property’s events and weddings manager.

Ms. Celiceo found the location while researching unusual wedding places. “Every nook and crevice had carvings and marking,” she said. “It smelled wet and earthy, and was peaceful and cocooning. You felt like you were in a different world, even though the rest of the world is happening above you.”

For their nuptials, many brides and grooms have been opting for unusual settings that speak to their love of nature and adventure, from cavernous sites to tree houses and nautical backdrops.

“Covid taught couples to ask for anything they wanted,” said Lindsey Shaktman, the director of planning and operations for Mavinhouse Events, a wedding planning firm based in Ipswich, Mass.

Bridal Cave offers couples a 15-minute ceremony for up to 40 guests for $1,195; the package includes an officiant, photographer and flowers. (At an extra cost couples can also have their reception at the property’s nearby Thunder Mountain Park Event Center.)

Tim Wood and Lauren McKenzie of Pittsburgh were married Aug. 10, 2024, at the Mohicans Treehouse Resort and Wedding Venue in a forest in Glenmont, Ohio.

“This wasn’t a lame, cookie-cutter hotel for $80,000,” said Mr. Wood, 32, who is currently in a doctorate program at the University of Pittsburgh. While touring one hotel, he said, he realized he had been there for a work conference. “That wasn’t the memory or experience we wanted,” he said.

Mr. Wood said he and Ms. McKenzie, a dietitian, “felt like we were in ‘The Hobbit,’” only with a cigar bar and dance floor, among their wedding amenities, and without cell service. “Lauren and I woke up to birds chirping,” he said. “I took an outdoor shower and felt the stillness of the world and watched this beautiful forest come alive.”

The 77-acre property they were at includes 10 tree houses and several overnight cabins and cottages for up to 95 guests, along with honeymoon suites. Prices start at $5,000. As is the case for many of these unconventional experiences, catering and other traditional offerings other than tables and chairs are not included.

The Mohicans Treehouse Resort hosts around 90 weddings a year, according to Laura Mooney, who owns the property with her husband, Kevin Mooney.

For a more intimate treehouse experience, there’s the Emerald Forest Treehouse in Redmond, Wash., which hosts up to 35 guests and is available from May through September. The owner, Scott Harlan, says he gets 150 requests a year for the $4,000 experience, which includes tables, chairs and decorations.

Two types of couples seem to gravitate toward these experiences, said Michelle Miles, the founder of the Sustainable Wedding Alliance, a British company that specializes in sustainable weddings. “Those who want Instagrammable, jaw-dropping backdrop weddings, which is why elopements are on the rise, and those wanting nature as their décor,” she said.

Nature-centric locations offer a mindful, social-sustainability perspective and leave less of a carbon footprint, Ms. Miles added.

Cindy McPherson Frantz, a professor of psychology and environmental studies at Oberlin College, understands the desire to be in a natural element. “Natural settings are good for fostering connection with the setting, and between people,” Dr. Frantz said. “Natural settings create a sense of awe, and awe is an elevating emotion that lifts you up and expands you.”

Two years ago, Ms. Shaktman of Mavinhouse Events planned a wedding ceremony for a couple in the middle of the Atlantic Ocean, off the coast of Salem, Mass. Their 220 guests witnessed the ceremony while free-floating from whale-watching vessels.

“The groom’s family, and the bride and her family, pulled up to the designated spot in their own boats,” Ms. Shaktman said. “Then the groom, who drove his family boat, picked up the bride, and that boat doubled as their altar.” Once vows were exchanged, the vessels that had circled the couple’s boat headed to Pickering Wharf Marina in Salem. Guests were later treated to a pizza party on the beach.

Weddings like these, Ms. Shaktman said, bring a heightened level of awareness and are “a once-in-a-lifetime experience” that everyone can be part of at the same time.

“There are no walls,” she said. “The Atlantic Ocean was their design; the Boston skyline was their backdrop.”

But, compared with more traditional wedding venues in ballrooms and hotels, such experiences can present some logistical challenges.

“A hotel is a one-stop shop — it’s easy, convenient and traditional,” said Carley Tryon, a founder of C&E Event Productions, a wedding events company in Westchester County, N.Y.

Two summers ago, Ms. Tryon organized a wedding ceremony and cocktail hour on Pollepel Island in the Hudson River Valley. On the island sits Bannerman Castle, an abandoned military warehouse that dates back to 1901.

The property, open May through October, has no electricity nor water, and is accessible only via ferries owned by Pollepel Island, which leave from docks at the train station in Beacon, N.Y. (Three locations on the small island are available for events: the warehouse; a courtyard, which has a garden and views of the river; and an indoor space, that once contained the owner’s home. Ceremonies for up to 40 guests costs $4,000 for weekdays and $5,000 for weekends.)

“We had to bring everything over ourselves by a boat,” Ms. Tryon said. Still, she added, “it was a beautiful event, in a primitive location, which was very different from anything we had planned before.”