Every Tuesday, Balboa Park rotates free admission across its seventeen museums — the San Diego Museum of Art, the Natural History Museum, the Fleet Science Center, the Museum of Us, and more. Which museums are free rotates by week. The park itself — 1,200 acres of gardens, architecture, and the world-famous San Diego Zoo nearby — is always free to walk. Check balboapark.org for the current week's free museum roster. The best value Tuesday in Southern California.