Frank Lloyd Wright's Hollyhock House in Barnsdall Park is a melange of architectural themes that surprisingly works. It was built for an oil heiress in the 20's and boasts Mayan flourishes, a hollyhock (flower) motif, and an inside moat.
The day I visited the house, they weren't offering any inside tours, so I just got a peek on the outside (which was still impressive). The park also holds an art museum and theater, but unfortunately everything was closed. Next time!
Tours are offered Wednesdays through Sundays and are $7 for the general public.