The Tiber (the third longest river in Italy)
Vatican City (Vatican Museum, Sistine Chapel)
Be warned; it’s really hot in August. And there’s no air-con in the Vatican. You’d think the pope might have made the effort but nope.
The Hop-On-Hop-Off Bus
Although when it’s over 40 degrees, there’s not much hopping off.
The Trevi Fountain (make sure it’s not closed; I was not amused)