Magic Fountain of Montjuïc

Designed by engineer Carles Buïgas for the 1929 Exposition, the Font Màgica sits at the foot of Montjuïc directly below the National Art Museum, and its evening shows, jets of water synchronized to music and colored lights, running on a schedule of several nights a week, remain one of Barcelona's most popular free spectacles, drawing nearly 92,000 reviews. The show typically lasts around half an hour and repeats a couple of times per evening, so there's some flexibility in timing a visit. Reviewers advise checking the schedule in advance, since it doesn't run nightly year-round. It's an easy, no-booking-required addition to an evening that might also include the MNAC steps above or Poble Espanyol nearby.