Amid the crisp, thinning mountain air steeped in the aroma of pine trees, a single-track trail winds through a dense evergreen forest past sweeping views of the valley below. In 2005, wilderness enthusiast Stefan Van der Steen founded Denver Adventures as a means of introducing others to scenes such as this by immersing them in the great outdoors through adventures such as ziplines, hiking treks, and rafting excursions. Stefan and his team of knowledgeable guides lead groups to an elevation of 8,000 feet for zipline tours on an Association for Challenge Course Technology–certified course, where riders reach speeds up to 50 miles per hour past Colorado’s naturally blurry trees. Denver Adventures also leads hiking, snowshoeing, and mountain-biking treks through the uneven terrain, gauging participants' skill throughout to determine whether they can traverse a steep uphill climb or do a Superman seat grab over a row of sleeping bears. Making use of all the wilderness has to offer, guides also take explorers on rafting trips through canyons and past gold mines, or train them to navigate vertical routes using top-rope techniques during five-hour rock-climbing excursions.