Subway Cave is a 20,000 year old lava tube near Old Station, California.  It is a popular landmark near Lassen Volcanic National Park, its 0.25 mile cave resembling a subway tunnel.  For many this is their first time ever in a lava tube.  There is however a section of the cave that is not often visited by the general public to which the cave extends another 1,000 feet.  The cave is in great shape, resembling a typical Hawaiian lava tube w/ a noticeable aa floor w/ rocks firmly attached to the bottom.  Only the vandals seem to leave there mark down this part of the cave, where graffiti abounds especially downwards towards the end.  Ceiling height here varies from six to ten feet.  The bright entranceway also has a separate passage to the left.