The San Diego Model Railroad Museum is a model railroad exhibit in San Diego, California. At 27,000 sq. ft., it is the largest such indoor exhibit in North America, and one of the largest in the world. The museum is located on the lower level of the Casa de Balboa Building on the Prado in Balboa Park. Nearly three million people have passed through the center since it opened in 1982. The San Diego Model Railroad Museum is a 501(c)(3) organization non-profit charity.