Spend a relaxing day exploring Caldes de Montboi, home to one of the hottest hot springs in Europe--the water comes out of the ground here at a piping hot 74ºC. Snap shots of elaborate mosaics in the city's historic Roman baths, stroll across an elegant Romanesque Bridge, and admire paintings by Picasso and one of his good friends, Manolo Hugué at the Thermalia Museum. Want to test the waters? You can visit one of the modern thermal spas for a small fee, or rinse your hands with the scalding water that bubbles out of Font de Lleó, a 1581 fountain.
Before you go, buy some carquinyolis, a traditional sweet similar to almond biscotti to eat on the way back.
Getting there: Rent a car, or hop a Sagalés bus weekdays from Barcelona city center.