Antonio Gaudi’s finest work and the culmination of his career was the unfinished Sagrada Familia Church. It is by far my favorite site in Barcelona and the most impressive architectural structure in the city (if not in Spain). If I’m lucky enough to live to its completion, I plan to return to Spain to see it in all of its amazing splendor (that and the completion of the Acropolis restoration in Athens are the two projects I hope to see most). Sagrada Familia's completed height is expected to be so immense that you will be able to see it above the city’s skyline all the way from the sea.