If you simply want to kick back without an agenda, go to welcoming Sitges, which has frequent 30-minute train service from Barcelona. With a much slower pulse than Barcelona, this resort town southwest of the city is a perfect break from sightseeing. Sitges has jet-set status, but it's hung on to its Old World charm while managing to be both family- and gay-friendly.
There are Modernista-style mansions here and a few worthy little museums, but I recommend just poking around the old town's whitewashed streets, crammed with cafés and boutiques. Then head for the water to soak up the sun, sea, and sand.
Nine beaches, separated by breakwaters, extend southward from town (the last three are intimate and cove-like). Stroll down the seaside promenade or rent a beach chair for some extreme relaxing. Along the way, you have your choice of restaurants and chiringuitos (beachfront bars) for tapas, paella, and drinks.
If you happen to visit during one of Sitges' two big festivals (St. Bartholomew in late August and St. Tecla in late September), you may see teams of castellers competing to build human pyramids up to 60 feet high.
Balancing on the shoulders of the people below, the castellers are judged by how quickly they can assemble and take down their people towers. No one is really sure how this quirky tradition got its start, but it's a perfect reflection of the region's team-building bent.
Skipping out of Barcelona for the day is easy. Whether you experience the sacred, the surreal, or the seaside, you'll return to the city recharged and ready for whatever it has in store.