Public water fountains
Free drinking water, on the street, in the cities that have a lot of it. Each page gives the count, how close the nearest ones are, and whether the water is safe to drink.
Why these cities
These are the cities where public fountains are common enough to plan around. Rome and Barcelona each have well over a thousand; Venice and Florence have fewer but concentrate them where visitors actually walk. A city with a handful of fountains does not get a page, because the honest answer there is to fill up before you leave.
Fountain water is the same supply as the tap, so the verdict for the city applies to both. The map covers every country we hold data for.