The Legion of Honor opens its doors for free on the first Tuesday of every month.

Perched dramatically above the Pacific in the Richmond District, the Legion of Honor is arguably San Francisco's most underappreciated cultural gem. Modeled after the Palais de la Légion d'Honneur in Paris, it houses centuries of European art, from medieval works to Rodin sculptures, all with an ocean backdrop that alone is worth the trip. On any normal day, general admission runs $17.

But on first Tuesdays? Free. No catch. No app to download. Just show up.

If you haven't been, here's what you need to know: go early. Free days draw crowds, and parking near the museum in Lincoln Park is limited. Muni's 18-46th Avenue bus gets you close, or you can take the 38 Geary and walk through the park. Pro tip — the grounds themselves, including the stunning Land's End trail nearby, are free every day and worth the visit even if the museum is packed.

First Tuesday. Mark your calendar. Bring the kids.