Empire Cave, Santa Cruz, California

Also known as the "Porter Cave(s)" for its proximity to UC Santa Cruz's Porter College, Empire Cave is a small series of marble caverns on the western side of the UCSC campus, slightly north of Santa Cruz, California. It is accessible either from the west, via the Empire Grade (road), or from the east via a series of trails from Porter College.

Empire Cave consists of three or four major caverns (one cavern narrows significantly in the center) and one minor one, connected by smaller tunnels. It is fairly muddy, even in dry weather, and can partly fill with water after a good rain; the water always drains quickly, however, although the mud stays for quite a bit longer. No parts of the cave are dangerous to explore; although getting to the last and smallest cavern is reasonably difficult, involving several awkward holds while in a prone position, it's pretty much impossible to pick up any injury more severe than a sprained ankle while attempting it. Belly-crawling through muddy tunnels, however, is to be expected; wear old clothes that can take some dirt or don't go past the first chamber.

Externally, Empire Cave is easily found and easily recognizable; it is located a hundred or so feet from Empire Grade, and capped by a large concrete block (legacy of one of the University's several attempts to seal it) with a sizable hole blown in it (legacy, or so I am told, of irate cave enthusiasts equipped with explosives). Entry is accomplished by climbing down a narrow shaft on a thirty-foot metal ladder. Although none but the most obese should have any problems getting down the shaft, it's still a good idea to watch your head.

Empire Cave is physically unremarkable. While some chambers, particularly the third cavern, do possess interesting flowstone outcroppings, none of the more spectacular rock formations associated with caves may be easily found. Marks of human contact are easily found, however, and range from the benign (faces sculpted into the mud in the last two chambers) to the vandalistic (graffiti on the walls of the entry shaft). The first chamber is in particularly bad shape; several broken planks and a nearly complete set of mattress springs, among other artifacts, have accumulated in one corner. The final chamber is a favorite location for hotboxing; marijuana and incense fumes, while not entirely unwelcome to some visitors, do linger in the cave for days and should be expected during any visit.

According to the San Francisco chapter of the National Speleological Society, at least two endangered species of arthropod have been found in Empire Cave; one or both, however, may now be extinct.

Sources:
personal experience
http://www.caves.org/grotto/sfbc/projects/empire.html