This is an area behind one of the openings of the Subway Cave. It is a 1/4 mile long lava tube on the north end of Lassen park.

A photo from the middle of the cave. In this section the ceiling is about 7 feet high. Other parts are a little under 6 feet high. The white patches are lime, the glowing orange object is the reflector for a self guided tour. There isn't anything green here - My scanner is failing a bit more than I can compensate for.