CDT Alpine Tunnel Loop

The loop typically starts from the historic ghost town of St. Elmo, Colorado. You'll find parking available in or near the town, which serves as a convenient base for beginning your ride.

The best time to ride is generally from late June or early July through September, once the high-elevation snow has melted. If you're looking for spectacular scenery, consider riding in the fall when the aspens and alpine tundra display vibrant colors.

The terrain is quite varied. You'll start with gradual climbs on smooth dirt roads and old railroad grades (doubletrack). As you ascend, it transitions to primitive singletrack, especially above treeline, which can be loose, rocky, and sometimes overgrown. Expect steep sections, including some hike-a-bike, particularly when climbing to the Continental Divide. Descents can be fast and fun on rocky, rutted roads, and later become smooth and flowy in the trees.

No specific permits or entrance fees are required to ride the CDT Alpine Tunnel Loop itself. However, it's located within the San Isabel National Forest, so always be aware of and follow general forest regulations regarding dispersed camping, campfires, and Leave No Trace principles.

This loop is generally considered to have a 'moderate' physical rating and a 'blue' difficulty for mountain biking, but it's not recommended for beginners. The high elevation (climbing to over 12,000 feet) and technical sections, including steep climbs and primitive singletrack, make it challenging. Acclimatization to altitude is crucial, and it's not ideal as a first ride in Colorado.

You'll encounter several unique features. The ride starts in the historic ghost town of St. Elmo. The route also incorporates the historic Continental Divide Trail and the Alpine Tunnel Trail, an old narrow-gauge railroad grade leading to the collapsed east portal of the Alpine Tunnel. You'll also enjoy endless views of alpine peaks above treeline and views of Tunnel Lake.

Yes, dogs are generally allowed on this trail as it's within the San Isabel National Forest. However, it's essential to keep your dog on a leash, especially in high alpine areas where wildlife is present, and to practice Leave No Trace principles by packing out all waste.

The loop is approximately 18 miles (28.6 km) long. Given the significant elevation gain (752 meters / 2,469 feet) and challenging terrain, it typically takes around 3 hours to complete, but this can vary greatly depending on your fitness level and how often you stop to enjoy the views or historical sites.

Yes, the route utilizes significant portions of the CDT - Colorado Section and Collegiate West trails. It also crosses sections of Tunnel Lake Trail, Tincup Pass Road, and Alpine Tunnel 4Wd Road, among others, offering a diverse riding experience.

Given the high elevation and remote nature, bring plenty of water, snacks, and layers of clothing as weather can change rapidly. A repair kit, first-aid supplies, and a reliable navigation device (like komoot with the offline map downloaded) are also highly recommended. Don't forget sunscreen and sunglasses for sun exposure above treeline.

The loop starts from St. Elmo, a ghost town with limited amenities. For cafes, pubs, and more extensive accommodation options, you would need to travel to nearby towns such as Buena Vista or Salida, which are about an hour's drive away.