Since a gift from David Rockefeller’s estate made it permanent, admission to the Harvard Art Museums is free for everyone, every day they’re open. Just off Harvard Square, the Renzo Piano-redesigned building gathers three collections — the Fogg, the Busch-Reisinger, and the Arthur M. Sackler — under one soaring glass roof, spanning European old masters, German modernism, and Asian art in a single visit.

That zero-dollar door changes how you use the place: drop in for twenty minutes with a single gallery, or settle into the light-filled courtyard between rooms without feeling you have to earn back a ticket. Open Tuesday through Sunday, it’s an easy add-on to any Harvard Square wander and one of the best free afternoons anywhere in Greater Boston.