The Spanish Steps, as they are popularly called, (Scalinata della Trinità dei Monti) form an expansive staircase that connects the Piazza di Spagna at the base and Piazza Trinità dei Monti at the top. The Spanish Steps are the longest and widest staircase in all of Europe. They are usually crowded as you can see from my picture above. From the top of the Steps you can see out over the famous seven hills of Rome.
During the summer, as I was lucky enough to witness, you can usually see newlyweds taking their wedding pictures while wading in the fountain at the center of the Piazza di Spagna. It is considered good luck to wade into the fountain and kiss as pedestrians toss coins into the fountain. Presumably, the kiss allows you to steal all of their wishes! I would suggest visiting the Steps in the evening and grabbing some gelato to watch the sunset from the top of the staircase.