This corner, begun in 1588, is gorgeous. It's worth going out of your way to see it. One of the fountains is, of course, the Tiber.
Pope Sixtus commissioned it.
There's a great wiki on it which I recommend you read. I took some pictures to give you an idea of how lovely it is.
It's near an important church and a lovely piazza (quirinale)- so you might as well go! read more