This mountain “house” went on for miles. They called it the longest house in history. It was. To build the Transcontinental Railroad through Donner Pass, workers blasted solid granite with nitroglycerin. In 1993, the line was abandoned because modern shipping containers were too tall. When the Central Pacific Railroad stalled at the Sierra Nevada mountains in the late 1860s, the solution relied on the grueling labor of thousands of Chinese immigrant workers. Their defining achievement was the Summit Tunnel (Tunnel No. 6), a 1,659-foot bore dug simultaneously from four faces using hand drills and explosives to chip through the rock. Punching through rock was only half the battle. Donner Pass routinely receives more than 30 feet of snow in a winter, which unleashed avalanches that swept tracks and workers away. To keep the rail line open year-round, the railroad constructed nearly 40 miles of heavy wooden snowsheds over the tracks. Travelers in the late 19th century joked about riding through the "longest house in the world," as the sheds blocked the mountain views for hours. Over the decades, the route underwent massive alterations. The wooden snowsheds—which were notorious fire hazards and trapped suffocating locomotive smoke—were gradually replaced by durable concrete structures in the 20th century. As train traffic increased, a second track (Track 2) was blasted through the mountains in 1925 on a slightly different, wider alignment to accommodate larger equipment. This historic route finally closed in 1993. Facing the immense cost of keeping two separate routes clear of snow, and unable to fit the tall double-stack containers through the 1860s bores, the Southern Pacific Railroad (now Union Pacific) completely abandoned the original Track 1 alignment and the Summit Tunnel. All rail traffic was consolidated onto the newer Track 2. Today, the original hand-drilled route of the Transcontinental Railroad sits silent. The abandoned concrete snowsheds and 19th-century granite tunnels have become a popular hiking route. Their walls are heavily covered in graffiti, and during the winter months, repeated freeze-thaw cycles turn the tunnel floors into a single, continuous sheet of smooth ice. Some go linear ice skating here.