This Barcelona attraction is easily one of the world's most unusual urban parks. It features buildings designed by famous Spanish architect Antoni Gaudi, whose work can be seen throughout the city. The whimsical structures (which were originally designed as part of a housing development that was ultimately unsuccessful) give Guell a slight theme park feel. The buildings cover only part of the park, with gardens and more natural areas covering the rest. The mix of cultural and natural elements makes Guell a good option for sightseers who want to take in some interesting design and nature while stepping out of the city landscape.