There's one question I often get in Rome: Is the water — especially from all those, yuck, public fountains — safe to drink?
The short answer: Yes. And it tastes good, too.
Rome's never been a city limited in water usage, as I wrote in my recent Guardian piece. By the first century A.D., thanks to the aqueducts, the city had 1,000 liters of water available per person, per day. Today, there are 500 liters available. Per family. Still, though, more than enough.
And lots of that water still freeflows out through the fontanelle (little fountains) placed around the city. (You might also hear these fountains called nasoni, after their nose-shaped spigots). The water's brought in from outside the city. It's safe. Fresh. Super-cold. So do as the Romans do: Save your €1.50 and refill your water bottle at the nasoni. There are 2,500 in the city, so you shouldn't have trouble finding them.
[Update, 2013: And just in case you did have trouble… there's now an app for finding fountains in Rome's city center! Oh, how things have changed in a mere couple of years.]
One last tip: If you plug up the end with your thumb, the water will spurt out of a handy hole on the top, providing you a makeshift water fountain. See, modern Romans are good engineers, too! Well, sometimes.