Pisa was a city in Italy. It was home to the Leaning Tower of Pisa. (TV: Dinosaurs on a Spaceship [+]Chris Chibnall, Doctor Who series 7 (BBC One, 2012).)
In 1190, Ben Daheer asked the First Doctor if he was from Pisa, to which he replied in the negative. (TV: "The Lion")
In the 13th century, the Eighth Doctor visited Pisa and stopped the Sulumian Thorgan from killing Fibonacci before the Italian had written the Liber quadratorum. (PROSE: The Gallifrey Chronicles [+]Lance Parkin, BBC Eighth Doctor Adventures (BBC Books, 2005).)
In the early 21st century, Brian Williams visited Pisa and sent a postcard to Amy Pond and Rory Williams. (TV: Dinosaurs on a Spaceship [+]Chris Chibnall, Doctor Who series 7 (BBC One, 2012).)