Knapp's Castle are ruins off of the 154 in SB: "The land was bought in 1916 by Montecito resident George Owen Knapp, a wealthy industrialist. It took four years to build the sprawling 100-ft long mansion, which was complete with pipe organ, observatory, dining hall, a long hallway, five bedrooms, and additional buildings such as a studio, cottage, servants' quarters, and superintendent's house. Twenty Italian stonemasons were brought in to build the castle. Water was pumped from several waterfalls on the eastern end of the land.
In 1940 the property was sold to Frances Holden who asked her friend, the famous Opera-singer Lotte Lehmann, to come and live there with her. Only five weeks later it was destroyed by a forest fire."
It's off of East Camino Cielo. It's mostly all paved road but a really cool hike out to the ruins, and there's plenty of fire roads up there...the trick is finding them
There's also a hot springs up in the foothills...there's a blog about the spot: Agua Caliente Hot Springs « Songs of the Wilderness
with pics, directions, etc.