Collserola is the green wall that stops Barcelona from going on forever — a whole forested ridge held as a natural park, ten minutes from the centre by train and a different country once you're in it. Four and a half kilometres of pine, holm oak, and one steel needle on the skyline.
Start at Baixador de Vallvidrera, an FGC halt that opens directly into the trees. Pause at Vil·la Joana, the house where the poet Verdaguer died, then pick up the broad track along the serra (ridge). The city shows itself only in flashes through the canopy; mostly it's birdsong and the soft give of the path.
The needle ahead is the Torre de Collserola, Foster's 1992 tower, and you can ride its glass lift to the deck if the hours line up — check first, they're short. Then bear down to the Pantà de Vallvidrera, a small old reservoir held in the woods, and sit a while by the water.
From there it's down through Vallvidrera to Peu del Funicular, where the funicular hands you straight back to the FGC and the city you'd half forgotten was there.
