There's no doubt that Barceloneta Beach is the most famous expanse of sand in the city. Instantly recognized by the towering, fin-shaped sculpture at the Olympic Port, you'll often see everyone from nude sunbathers to vacationing families waltzing through the surf both day and night. Because of its proximity to most of Barcelona's central attractions, the beach is usually incredibly busy, especially on the weekends when the bars, clubs, and restaurants maintain their popularity into the night.
Once the late evening hits, wander the oceanfront to find yourself at some quality clubbing establishments like Shoko, Opium, and CDLC, all of which are located together near the Olympic Port on the Passeig Marítim. These are more exclusive clubs that will have people queuing outside the door on the weekends, so dress up and be prepared to pay a decent cover. Cheaper, less pretentious alternatives are scattered around the more condensed Barceloneta neighborhood to the south, led by hole-in-the-wall Bar Leo and popular promenade-side Santa Marta.