A growing number of tours let visitors explore the elevated ecosystem of the rain forest canopy, a luxuriant and little-known realm that is home for most of the jungle's plant and animal species. It has only been in the last two decades that biologists have begun to seriously study the canopy, using such varied devices as mountain climbing equipment and construction cranes, and tourists now have the opportunity to follow them into that biological frontier. Those opportunities range from a ride on a modified ski lift that takes passengers floating through the tree tops to platforms set in the crowns of massive tropical trees, more than 100 feet above the jungle floor. All those tours offer a monkey's-eye view of the rain forest canopy, where thick branches serve as platforms for an incredible diversity of smaller plants, and such animals as tree frogs, vine snakes, sloths and hundreds of bird species. Adventurous travelers may want to try one of the more rustic canopy tours, which entail strapping on a mountain climbing harness and pulling yourself along suspended cables to a series of small wooden platforms built in the tops of trees. Several private biological reserves also have platforms in the canopies of large trees that people are simply hoisted, or hoist themselves, up to. One private reserve even has a small hotel room built in the top of a tree, for those who want to spend a night in the canopy.