Say you were inviting a friend to visit Austin. Would you let them leave without visiting Barton Springs? Didn't think so. Do yourself a favor, then, when you arrive in Barcelona: head straight to Parc Güell.
Perched atop a hill in the north, central part of the city, Parc Güell offers a breathtaking panorama of Barcelona's cityscape and its Mediterranean coastline. To reach Parc Güell from Central Barcelona, take the green line (L3) to the Lesseps Metro Station and follow the signs. You'll know you're on the right path if you get on an escalator--yes, there is an outdoor escalator in Barcelona--and climb more flights of stairs than you can count.
"So," you're saying, "it has a nice view? I can see the 360 Tower from Barton Springs. That's not why I go". Fear not, my friend. Designed by iconic architect and one of the most notable figures in the history of the Catalan Independence movement, Antoni Gaudí (1852-1926), Parc Güell features castles, benches, houses, and even a medium-sized dragon made of multicolored mosaic tiles. Serving as a party house for his many important guests during his lifetime, it now serves as a source of wonder for Barcelona visitors young and old, acting as a complement to Gaudí's many wonders across the cityscape, including the Sagrada Familia cathedral, which has been under construction since 1884 and is not slated to be finished until 2026, perhaps later.

It's appropriate that Gaudí's work is so integral to the personality and aesthetic of Barcelona, as Gaudi was an outspoken proponent of the Catalan Independence movement, which advocates the independence of Barcelona's Catalunya province. It's probably a good time to mention that while Spanish and English are both understood and used in Barcelona, Catalan is the official language, a strange hybrid between French, Spanish, and Italian that will probably leave you scratching your head when you see it all over the city.
What do you do in Austin after you finish taking a dip in Barton Springs? Personally, I head over to the Barton Springs Saloon and enjoy some of their killer drink specials. Some may head to Home Slice Pizza. Others, still, will head to Zilker Park for some disc golf. Barcelona, too, affords visitors the option to indulge in almost countless activities, from navigating the pedestrian zoo of La Rambla, shopping on the cosmopolitan Avenida Diagonal, dining in seaside Barceloneta and lounging on its beaches, or even seeking out the remainder of Gaudí's work throughout the city. Whatever you do, make sure and start at Parc Güell, and this writer even happens to recommend ending there--its panorama will afford you the opportunity to wrap all your Barcelona travel memories into a nice package right before your eyes.