Basílica de la Sagrada Família is one of the brilliant works of Gaudí's fairytale architecture. Basílica de la Sagrada Família is a UNESCO World Heritage Site and is visited by five million tourists each year.
Trevi Fountain in Rome, Italy -- "the fountain at the junction of three roads." Throw a coin into the fountain, and legend has it that you will return to Rome. I wish I'd tossed a coin in while I was there!