In a hot summer like this one, in 2017, a reference point for tourists, more important than a map not to be lost among the many streets of Rome, are the little fountains (fontanelle), always available with fresh, free water of high quality in any moment.
They were introduced in 1874, with three ventilation holes in the form of a dragon (one of them is still present in the Piazza della Rotonda behind the Roman Forum), and then replaced by a single nozzle, for this reason nicknamed "nasone" (big nose).
The mouthpiece of all "fontanelle" has a small hole in the upper part. Covering with one finger the main outlet of the nozzle, the water gushes upwards; a little trick, and the drink becomes easier and more hygienic.
More than 2,500 "nasoni" (more than 200 inside the walls of the center), plus hundreds of sources of different shapes, which offer water at any time, is a vital help for anyone who needs it.
On the site https://www.acea.it/en/group you can find the nearest "nasone" from where you are