/ Along the Mediterranean shore of eastern Spain lies Barcelona, one of the great cities of Europe to put high on your list of places to see. Although its sprawling metropolitan area is home to 4.2 million residents, you can easily see the main attractions of this country's second-largest city in just a few days by walking through its square-mile historic center. And be sure to see Barcelona's most famous building, Sagrada Familia, the fantasy church designed by that eccentric architectural genius, Gaudi.