There is a gem on the plaza in Old Town San Diego: the Casa de Estudillo. One of the oldest adobe houses in the oldest town in California, Casa de Estudillo stands alone. Built in 1827, it has a rich history steeped in the spanish heritage of the early settlers of this land. Lovingly restored in 1910, it opened as one of California's first historic tourist attractions and helped inspire a movement throughout the state to preserve such relics of the past. To add to the home's unique charm, it's rumored to be haunted. San Diego Ghost Hunters has conducted several investigations there over the years.
http://www.sandiegohistory.org/journal/v50-1/una_casa.pdf