Switzerland Trail, Historic trail in Boulder County, Colorado.

The Switzerland Trail follows the roadbed of a 3 ft (914 mm) narrow gauge railroad, about 30 miles (48 km) long, winding between altitudes of 7,000 and over 9,000 feet from Eldora past Nederland and Sugar Loaf to Ward. The railbed is typically 8–10 ft (2.4–3.0 m) wide, and a broad band of closely packed light grey stones laid flat marks the route.

The route was built in the late 1800s as a narrow-gauge railroad to connect mining settlements like Gold Hill and Nederland. It carried materials and people between these mountain communities along what became the Denver, Boulder and Western Railway.

The name "Switzerland Trail" was coined by the Colorado and Northwestern Railroad in 1898 to draw tourists, and the railroad built park sites and hotels such as Mont Alto to attract day-trippers from Boulder and Denver. The west end is listed on the National Register of Historic Places as the Denver, Boulder and Western Railway Historic District.

The surviving roadbed runs about 30 miles (48 km) from the Eldora townsite past Nederland and Sugar Loaf to Ward, climbing between 7,000 and over 9,000 feet. The railbed is typically only 8–10 ft (2.4–3.0 m) wide, so users share a narrow corridor. Its 2%–5% railway grade makes the route easy to walk or ride, and the west end lies within the Denver, Boulder and Western Railway Historic District.

The railbed is typically only 8 to 10 feet (2.4 to 3.0 m) wide, so users pass close to the surrounding terrain. Its 2% to 5% railway grade is what makes the route easy to traverse today.