Aletrail in San Francisco

A promotional sun clock on the site of San Francisco's great raceway.

A huge musical instrument played by the ocean.

Gold Rush-era tombstones line the park's paths.

An art supply shop holds the secrets of this quiet neighborhood's raucous Barbary Coast past.

A 300-ship graveyard, with a few still visible at low tide.

A modern mechanical planetary system, part of a 10,000 year clock.