HIGHS: “Our treehouses are discreetly tucked away in the forest, in the boughs of ancient mahogany trees,” says Trevor Saxty, president of California-based Adventure Center (adventurecenter.com), which offers camping excursions throughout Africa. For $275 per night, tourists can sleep in a timber treehouse overlooking Tanzania’s Lake Manyara National Park, famous for its tree-climbing lions (not to worry: they climb only acacia, not mahogany trees).

In 1996, inspired by a class on human-environmental relations, Hawaii-based architect Dave Greenberg designed four tree houses near Hana, Maui. Two years later, he expanded his business to the island of Hainan, in the South China Sea (treehousesofhawaii.com; 86-1380-7500-909). The result is a small group of secluded cabins overlooking some of the world’s most pristine beaches. On Hainan, the houses perch in tamarind trees that sprout from –a sand dune. They overlook a beach and adjoin the 5,000-acre Sanyan Nashan Buddhist temple and park, filled with pagodas and botanical gardens. A treehouse on Maui costs $125 per night; in Hainan it’s $43.

At St. Lucia’s Ladera Resort (www.ladera.com; 758-459-7323; starting at $295 per night), rooms in the rain forest perch 1,100 feet above sea level, and guests should expect unexpected visitors. In the morning, it’s not uncommon to wake up and find a fluorescent green parrot flying through your room or a friendly lizard near your makeup case, says general manager Magnus Alnebeck of the three-walled, open-air rooms.

Across the EU, it is still illegal to sleep overnight in trees–or anyplace not specifically built as an accomodation. But the 2003 Alan Rogers Western Europe camp guide lists a resort in Holland where balloon-like tents hang from trees just six feet above the ground. “This is as close as we can get to a treehouse,” says Rogers.

LOWS: For guests who want to travel closer to the ground–or spend time in it–Adventure Center also offers caving expeditions. The 15-day, $760-per-person Ancient Carthage and Camel Desert trip takes campers through Tunisia, where they visit the fourth-century village of Matmata and sleep on goat-hair rugs in caves with a Berber tribe.

Ian Anderson’s Caves Branch Adventure Co. & Travel Lodge (cavesbranch.com) in Belize offers trips to more than 60 caves, with one- and two-night stopovers that allow guests to sleep 600 feet underground among Mayan artifacts and skeletal remains. “Life is as it was 2,000 years ago,” says Anderson. “There is no sun, no wind, no flooding.” A perfect Halloween holiday.