For magnificent 360-degree Barcelona views, head to the El Carmel neighbourhood (under a kilometre east of Park Güell) and up the Turó de la Rovira hill to the Bunkers del Carmel viewpoint. Above the weeds and dusty hillside, you’ll find old concrete firing platforms where students and visitors gather, especially at sunset. The platforms were part of anti-aircraft battery during the Spanish Civil War; postwar, it was a shanty town until the early 1990s, and has lain abandoned since then.
There's a small information centre/museum inside the bunkers themselves; placards give an overview of what once stood here. Buses run here from central Barcelona; from the nearest bus stop in El Carmel, it’s a 10-minute (600m) walk east to the viewpoint.