Your tree house was pretty great when you were 10, but a growing number of tree hotels are upping the ante.

Tree climbing “has become a vacation destination due to some strange combination of childish nostalgia, eco-awareness and an appreciation for the spider-like thrill of swinging from ropes,” reports the Wall Street Journal. “Who climbs trees?” writes Benjamin Percy, the author and a climber. “Plenty of people.”

In the United States, the Pacific Tree Climbing Institute in Eugene, Ore., offers guided tree-climbing expeditions, including overnight stays in the green canopies of the Pacific Northwest. Elsewhere, Treehotel in Harads, Sweden, offers rooms between 13 feet and 20 feet above the ground. Cockatoo Hill Retreat in North Queensland, Australia, hosts guests in tree houses on a ridge 230 feet above the Coral Sea.

These aerial treks borrow heavily from rock climbing: Climbers are clipped into nylon safety harnesses. They wear helmets. They scurry upward, moving quickly over smooth bark and slowing down when they reach thick branches hundreds of feet in the air.

From a perch 100 feet above the ground, Percy observes, “The only thing that keeps me from plummeting to the forest floor is a braided nylon rope as wide around as my finger. It is anchored to the top of a 500-year-old, 250-foot Douglas fir.” It takes, he writes, an hour and a half to summit the tree. “I loop an arm around the trunk and imagine myself as an eagle in a roost.”

The Oregon institute is run by arborists Rob Miron and Jason Suppa, who provide canvas hammocks for intrepid climbers willing to spend the night in the “ultimate air mattress.”

In the morning, the climbers prepare to descend. For some, breakfast awaits on the ground below. As Percy descends, his body gently plunges downward and he recognizes an unmistakable feeling as he takes a glimpse around. “It’s the giddiness of childhood.”