Nob Hill's heavyweight hood ornament is a must-visit for those intrigued by cathedrals and architecture. In addition to stunning stained glass, there are two meditation labyrinths (outside and in), and three massive organs.
The Episcopal congregation's historical roots go back to the California gold rush, and with a progressive approach to religion ("A house of prayer for all people, without exception") the organization enjoys widespread local support.
One of the best times to visit Grace Cathedral is during one of their (frequent) musical events - check the schedule!
Address: 1100 California St, SF, CA
Website: http://www.gracecathedral.org/calendar/overview/musicevents/
Wikipedia: http://en.wikipedia.org/wiki/Grace_Cathedral,_San_Francisco