Amboy Crater is an extinct cinder cone in the eastern Mojave Desert of southern California, rising from a broad lava field within Mojave Trails National Monument near Amboy and historic U.S. Route 66. Formed during the Pleistocene and estimated at about 79,000 years old, it contains a solidified lava lake and stands above surrounding basalt fields. For much of the 20th century, its unusual volcanic form made it a popular Route 66 stop and memorable desert landmark. Visits declined after Interstate 40 opened in 1973, but later revived. Also designated a National Natural Landmark in 1973, it remains a notable geologic and tourist destination.