Angel Island, which used to be,
among other things, an army base and an
immigrant detainment facility,
is a large island in San Francisco Bay with 750' of topography. You can
take a (pricy) ferry to go there. While I wouldn't do it every day (crowded,
costly, time-consuming), I'm glad we got out here at least once. A circuit
around the island yields great views of north SF Bay and environs. It gets a
bit hot here in the summer.
They even used to have a Nike ground-to-air missile battery high on Angel
Island, SF-91.