I don't know if you'd want to walk on the Golden Gate bridge naked but
there's a beach next to the old fort under the south end of the bridge
where people skinnydip.

Engineman

You might want to take a walk on the Golden Gate Bridge, too. There's
a frightening amount of steel in that thing which you pretty much miss
if you drive over it. Walking it naked, outside your car, you can
sense a lot more of the grand scale of the beautiful thing, too.
http://goldengatebridge.org/visitors/directions.php