The UFO is a far-out tree house offering from Sweden's Treehotel. The exterior is made from "durable composite material." Inside, it can accommodate up to two adults and three children.
Free Spirit Spheres/Facebook
Pitched to folks who like to glam it up while camping (aka "glamping"), Free Spirit Spheres' spherical lodgings are strung from three trees each, a concept that the company says "borrows heavily from sailboat construction and rigging practice." There are three units in all, two made from wood and one from fiberglass.
'Round room of wonder'
A graphic designer in New Zealand built this "tech tree house," the Skysphere, from scratch for $50,000 in materials and a mere 3,000 hours of work. It's solar-powered and Android-controlled, and has a "refrigerated, in-couch beer dispenser." About the only thing it doesn't have right now is a bathroom.
Located in the piny village of Harads, Sweden, the reflective-glass-covered getaway, roughly 13 by 13 by 13 feet, is one of seven "tree rooms" available for lodging at the Treehotel (including the UFO earlier in this gallery).
And, yes, there's Wi-Fi.
Nelson Treehouse and Supply/Facebook
A room with a lot of views
The Glasshouse Treehouse in New York's Catskill Mountains was constructed, in part, with salvaged windows.
Fit for James Bond
Blue Forest, a UK company that builds custom, luxury tree houses, calls this one the "High-Tech Hideaway." It was designed for a Greek customer who requested a 007-style retreat for his children. It comes complete with an entertainment center and a "a state-of-the-art biometric security system."
The unit is more than big enough to accommodate two adults. It holds up to 2.3 tons.
Guy Mallinson Woodland Workshop, Crafty Camping & The Woodsman's Treehouse/Facebook
Six figures of fun
Described by NBC as the "$200,000 tree house," the oak-nestled Woodsman's Treehouse in Dorset, England, features a rope bridge to the entryway and a spiral staircase to a roof deck that looms some 30 feet above ground. There's a sauna, a hot tub and even a pizza oven.
This unique Airbnb rental in northwestern Germany sits about 10 feet above a pasture. Jojo, as the stilted tree house is called, can accommodate up to 12 people. Wi-Fi and an iPad are at your disposal.
Arctic TreeHouse Hotel
It's not always snowy in Rovaniemi, Finland, but when it is, the tree-house suites at the Arctic TreeHouse Hotel are especially picturesque.
Billed as the Bel Air Treehouse, this $1,000-a-night Airbnb rental has Wi-Fi, a chef's kitchen and skylights.
Agriturismo La Piantata B&B/Facebook
Under the Tuscan sun
The 936-square-foot, luxury Black Cabin is one of two tree houses at La Piantata, a bed and breakfast on Italian farmland between Siena and Rome. You'll find it in a 200-year-old maritime pine, about 23 feet above the ground.
Up in the air
The pod-shaped Redwoods Treehouse in Auckland, New Zealand, is situated about 33 feet above ground in the huge tree from which it takes its name. It's available for rent, with the capacity to seat 30 guests for corporate events or weddings.
There are a lot of selling points for this Airbnb rental. Our favorite? It features a hot tub up in the trees.
The Majestree, soaring nearly 50 feet above the ground with the help of a stately Douglas fir, is one of more than a dozen treehouses at Out'n'About, a bed-and-breakfast "treesort" in Cave Junction, Oregon, near Siskiyou National Forest. Be prepared to climb four sets of stairs in all, and cross two suspension bridges, to access it.
Mark Kolbe/Getty Images
South Pacific style
Lupe Sina Treesort bills itself as the "first and only authentic, luxury, tree-house hotel in Samoa."The Samson Suite climbs nearly 40 feet in the sky, thanks to an ancient banyan tree; the Star Gazer is poised about 32 feet above ground.
Located in the woods of Bolt Farm, The Majestic is a 40-acre spread in Walhalla, South Carolina, designed by Seth Bolt of the Grammy-nominated band Needtobreathe. Available as an Airbnb rental, the tree house is off the grid (no Wi-Fi or even cable TV) and that's fine. You're supposed to stare at the windows, not a screen.
Swing on by
In Banos, Ecuador, the star attraction of the for-rent La Casa del Arbol -- literally "the tree house" -- is the "Swing at the End of the World." It lets its brave user hang out over the Tungurahua volcano, some 8,500 feet above sea level.