In the middle of a tangle of mansion-laden, suburban streets, the graffiti-covered, half-finished lava house seems a bit out of place.

Few people know how it got there, but it was the local teenagers who christened it, thanks to heaps of lava rocks strewn about the property. Built by Jerry Ganz (the fabulously wealthy man responsible for the mass production of seat-belts) in the 1970s, the Lava House's chief architectural pull was its extensive use of imported lava rock. Construction stopped suddenly shortly after construction began, and it has remained empty to this day.

The City of Tiburon has tried desperately to sell it off, even razing what was left of the structures there after a 1997 fire to attract more buyers, but to no avail. It is mostly used these days as an impromptu party locale or a haunt for photographers trying to get a good view of the Bay, but exploring the maze of steep staircases, hidden subterranean rooms, and twisting balconies is also popular, both by night and by day.

Theories abound as to what made Ganz stop construction, mostly concerning the cost of the lava rock import coupled with the enormous size of the house. Others claim Ganz was importing the lava rock illegally and was caught. The most fantastic explanation involves the god of the volcano from whence the rock came cursing Ganz' workers for stealing pieces of his home, causing several of the contractors to die in freak accidents and eventually halting construction.

Volcano god or no, visitors do have to beware the police, as the Lava House is technically private property.