Alto Tunnel is an old railroad tunnel that once served the North Pacific Coast Railroad. Long abandoned, most of the rail right-of-way has been turned into multi-use pathway in Marin County. These paths are part of Ecorings Initiative called the Sonoma Marin Adventure Trail stretching 84 miles from Sausalito on Richerdson Bay to Cazadero in the Redwoods north of the Russian River. The segment from Sausalito to Larkspur and the segment from Corte Madera to San Anselmo are separated by the closed Alto Tunnel. The Alto Tunnel is a high-priority link in the Sonoma Marin Adventure Trail. We recommend that you visit the website of the Friends of the Alto Tunnel and sign up for messages on how you can support the reopening of the Alto Tunnel. View a video and learn more about the Alto Tunnel and how the Cal Park Tunnel was reopened here.