San Diego Model Railroad Museum

On the lower level of Casa de Balboa, across from the park's lily pond, the museum packs 27,000 square feet of layouts depicting Southern California railroading, from the Cabrillo & Southwestern to Southern Pacific's run over the Tehachapi Pass. As many as 50 trains run at once across three miles of track, with recreations like the Carrizo Gorge down to miniature graffiti painted on the freight cars. It's the only model-train museum in the country with AAM accreditation, and San Diego residents get in free on Thursdays.