Built in 1816 as a gristmill for the San Gabriel Mission, the mill is one of the last remaining examples in Southern California of Spanish Mission architecture. The thick adobe walls and textured ceiling rafters give the interior a sense of quiet strength. Be sure to step into the back room, now a gallery with rotating quarterly exhibits. Outside, a chipped section of the mill's exterior reveals the layers of brick, ground seashell paste, and oxblood used to hold the structure together. The surrounding gardens are reason enough to visit, with a flower-decked arbor and old sycamores and oaks. In summer the California Philharmonic ensemble performs in the garden.