Mantua
Mantua was a city in Italy, on Earth.

When The Doctor added the ability to daydream to his program in 2376, he imagined himself performing "La donna è mobile" to the  crew in the mess hall. He introduced his performance thus:

"Somewhere, in that totality known as the universe, is a galaxy called the Milky Way. Tucked into the corner of that galaxy is a planet named Earth. On that planet is a city called Mantua. Go straight ahead past the fountain, turn right, then left, then right again. You'll find yourself walking along the water, listening, as a man sings of his beloved's unfaithful heart, and even the fish begin to weep."
"Quando, la donna e mobile..." ()

External link
 
it:Mantova
nl:Mantua
de:Mantua
Earth settlements