A soaring new aspen has sprouted in downtown Denver. The striking hotel Populus, opened in October, embodies Colorado’s iconic tree inside and out, from the biophilic design by Studio Gang to the warm and woodsy hues of the lobby that brighten as you ascend, mirroring light-splintered foliage, and culminating in the rooftop bar Stellar Jay, which flourishes with regional flora. Looking for the parking garage? There isn’t one, its absence meant to encourage walking and the use of public transportation. Nearly every element is similarly considered to support Populus’ aim to be the nation’s first carbon-positive hotel. The windows have “lids” that shade the building; an on-site biodigester composts 100% of food waste; and reclaimed materials throughout include Beetle Killed pine and Wyoming snow fencing. Oh, and your room key? It’s made of wood, and it’s covered by a sleeve containing wildflower seeds that you can soak in water and plant. Forget elevator music: here, you’re serenaded by bird songs recorded in Rocky Mountain National Park. The sylvan theme continues in the earthy rooms, showered in natural light, with special touches like pressed wildflower artwork and hammock benches. Populus is the latest showpiece developed by Denver’s Urban Villages, a real-estate development and property-management company whose mission is to “bring nature back into our cities.” To offset the equivalent of Populus’ embodied carbon, 70,000 trees were planted in Gunnison County in partnership with the U.S. Forest Service. This will continue for the lifetime of the 265-room hotel: the carbon footprint of the interiors, from lighting to utensils, is monitored by an outside firm to determine continual plantings. In addition, guests are invited to participate in the One Night, One Tree program: for every night you stay, Populus plants a tree