Cal-a-Vie, on Gopher Canyon Road in Vista, offers 32 Mediterranean-style villas spread over 200 acres. According to its website, the 30-year-old spa "combines luxurious European spa philosophies with the California concepts of fitness, health and nutrition."
The top-ranked U.S. destination spa was the New Life Hiking Spa in Vermont.
The ranking was part of Travel + Leisure's 2016 World's Best Awards, compiled from a reader survey of top cities, hotels, airlines and cruise operations. Readers were polled between November and February.
For destination spas, readers were asked about accommodations and facilities, treatments, service, food and value.
The Rancho Valencia Resort & Spa in Rancho Santa Fe was rated the 50th best hotel in the world, the 15th best in the U.S. and fourth in California.
The winners in those hotel categories were the Nihiwatu hotel in Sumba, Indonesia; The Lodge at Glendorn in Pennsylvania; and the Farmhouse Inn in Sonoma County, respectively.
No other area hotels were on the list.
San Diego also missed out on a list of the top 10 U.S. cities. San Francisco, at No. 6, was the only California municipality included. The top- ranked city was Charleston, South Carolina.