The Diego Sepulveda Adobe gives Costa Mesa a rare visible link to its rancho period. The restored adobe stands in Estancia Park and tells the story of the old estancia, the Sepulveda family, and the layers of Spanish, Mexican, and early Californian history beneath suburban Orange County.
It is a small site, but a worthwhile one if you are already in Costa Mesa or nearby Newport. Visit when the historical society has it open, then walk the park to get a sense of how little of this older landscape survives.