Q: We'll be flying to California in June and plan to rent a car and explore. Can you tell me something about the old Spanish missions? We'd like to visit some. A: If you started in San Diego and drove north, you could spend a whole vacation going from mission to mission. You could stay at Clint Eastwood's hotel/restaurant on part of the Carmel Mission property and visit William Randolph Hearst's "Castle" at San Simeon, on land that was once San Miguel mission. The 21 missions built by Spanish Franciscan friars in the late-18th and early-19th centuries are strung out for 600 miles from San Diego to Sonoma, meant to be a day's horse back ride apart along the Camino Real, the King's Highway, roughly the route of today's U.S. 101. They're beautiful adobe and brick buildings with red-tiled roofs, weathered arches, bell towers and handsome colonnades, dressed up with fountains, grape arbors, trees and flowers. Some remain churches or schools, some are replicas or restorations used as museums, and some have disappeared. They weren't built in order, south to north. San Diego was the first and Carmel, several hundred miles north, the second. Settlements grew up around the missions or the nearby presidios set up for soldiers assigned to protect them and became the nucleus of today's cities -- San Diego, San Francisco, Santa Barbara, Monterey, Carmel, Sonoma, Capistrano, San Luis Obispo, San Jose. The missions had a big, beneficial influence in the settling of California. But don't tell that to a Native American. Before the friars arrived, Indian culture flourished in California. But by 1805, more than 20,000 Native Americans lived at the various missions, few willingly. They became virtual slaves. Nevertheless, the mission trail today, including San Simeon and Mr. Eastwood's ranch, is fascinating to tourists, even those who regret what happened to the Indians. For information on the missions, write to the California Office of Tourism, 1121 L St., Suite 103, Sacramento, Calif. 95814. Admission is free at most missions, although contributions are welcomed.