Parents, PJs and champagne

“How surreal is this?” was all Samantha Smith could think. It was midnight on a blustery fall night, and the flannel-clad accountant was standing alone at the top of the Queen’s Staircase at Hampton Court Palace in London, about to turn in for the night. “How many gorgeous women have come down this staircase in all their finery?” she recalls, “and there is me in my PJs.” The palace, which has played host to Henry VIII and his wives, as well as Shakespeare and his acting company, was home in September to Smith and 60 others who had paid $160 each for the pleasure of doing something most visitors wouldn’t dream of—staying the night.

After years of offering sleepovers to groups of excited children, now museums, aquariums and historic venues are expanding their programs and offering adult-only overnight visits. While kids get behind-the-scenes tours and meals, grown-ups get added perks, including champagne receptions and lectures from experts—some on themes not suitable for kids. At its annual Hugs & Fishes event on Valentine’s Day, the Vancouver Aquarium’s sleepover had talks revolving around the sex life of sea creatures. “Barnacles are a little kinky,” says Sue Murray, its sleepover manager.

While that Vancouver event goes back to 1996, most museum sleepovers for adults began more recently. The newest is Hampton Court Palace’s; its first test event was in the spring. “We learned people weren’t here to sleep,” recalls Kate Minchin, the visitor experience manager. So in September, they packed more into an Elizabethan-themed experience including period dancing and dinner in the Privy Kitchen, as well as entertainment provided by a troupe of actors. After a few hours bedding down in the magnificent Cartoon Gallery, visitors could take a garden tour at 7 a.m. One guest, Frances Murray, a South African initially skeptical of the concept—“I’m going to sleep on a hard floor for £100?”—was won over by the royal B & B. “How often do you get to do this?”

The sleepovers are part of a fast-growing trend of cultural institutions offering “value added” events. Exclusivity comes with price tags to match. Sleepovers start at around $100 and go up. Yet because most places offer no more than four a year, they usually sell out.

“People want to have a deeper, interactive informational experience,” explains Scott Black, specialty tour manager at the California Academy of Sciences in San Francisco, which started adult overnights in 2011. A recent one featured 40 post-doctoral students showing off their research—and wild cats, including an ocelot and a cougar. Unexpected things can happen. When one staff member at Dover Castle, the 12th-century fortress on the English Channel, discovered that a guest staying in its Great Tower was interested in graffiti, the visitor was taken to see the scrawls painted by 18th-century prisoners of war.

While Dover Castle provides camp beds for its sleepovers, accomodation is more basic at other sites—usually carpet, a thin mat or an air mattress brought by guests. For visitors, it’s the spectacle that counts, not sleeping comfort. At the Georgia Aquarium in Atlanta, visitors can lay sleeping bags down in an acrylic underwater tunnel of the Ocean Voyageur exhibit, watching whale sharks, manta rays and thousands of fish through its thick transparent walls. At Vancouver Aquarium, the view is of beluga whales. When staff turns off the lights in the gallery, “all of the sudden this massive creature at the window is staring at them,” Murray says.

Most venues use self-contained areas so visitors can’t wander off, but that wasn’t an option at the sprawling Hampton Court Palace, which has around 1,000 rooms. “The potential to lose people is mammoth,” says Minchin. So four warders, wearing wool frockcoat uniforms, escorted them to the toilets downstairs, off an open courtyard.

And guests were warned that professional photography and ghost hunting were forbidden, and told they should dress warmly in the unheated palace. The biggest problem turned out to be a “person who snored like a warthog all night,” Smith recalls. Even the earplugs that were handed out couldn’t overcome the noise.