On the way home: wine and a mission
Mile 76.6: Turn left to enter Calera Wine Company. Josh Jensen makes outstanding Pinot Noir in a multi-tiered structure that cuts into the hill like stairs. There's a pouring table inside (call ahead for tasting); a picnic table out front offers views of the green hills.
Mile 78.4: After returning to the main road, you don't have far to go before stopping again for the turnoff to Pietra Santa and DeRose vineyards, which share a common driveway. DeRose, with vineyards going back to 1854, has great Zinfandel and a casual tasting area in a barrel room; next door is the owner's impressive vintage car collection, including rare 1920s and '30s Graham-Paiges (call first).
Pietra Santa Winery is much more formal; the grand Spanish colonial-inspired tasting room has massive wood doors and a tower. The winery produces good Italian-style Sangiovese, plus organic olive oil from its trees.
Mile 83.6: Looking across Hollister, this point on Cienega Road provides the best overall view of the route. From here, you'll wind downhill into San Juan Bautista.
Mile 86.1: Take a left to stay on Cienega, then a left onto Union Road.
Mile 91.2: Head left onto State 156/San Juan Bautista Road; cross San Juan Creek.
Mile 95.5: Turn right on Alameda/Third Street toward downtown San Juan Bautista, the small settlement established by Spanish missionaries in 1797. The mission building and church, still home to an active congregation, have beautiful Spanish colonial lines, and there's a garden of heirloom roses.
San Juan Bautista's main drag, Third Street, draws tourists to its handful of antiques and art shops (check out Galeria Tonantzin and Mr. B's Z-Place). The town remains rural, though ― roosters and chickens still walk the streets. For dinner, try the Basque eatery Matxain Etxea for hearty lamb stew.
If you're lingering late in San Juan Bautista and home seems far away, your best bet for an overnight is the Posada de San Juan, in a historic building downtown. Or, to head back to U.S. 101 and finish the loop, drive 3 miles west on State 156 for a total of 98.5 miles.