Little Venice

Little Venice (リトルヴェニス) is an artificial sluice formed by numerous canals located in London, United Kingdom.

Principles
From the name, one can rather easily discern that it is based on the city of water. There are some large differences - the surrounding scenery is different from that of Venice and it is not a floating city, just a pier with three canals gathered at it. However it fully duplicates the artificial, magical effects in Venice which allow for heavier use of the terrain.

Background
Little Venice's construction was partially to duplicate the artificial, magical effects of Venice which allow for heavier use of terrain, though very few people know about it.

Acqua of the Back Arc
Archbishop Laura Stuart was having a boat ride in Little Venice when she received a report from the boatman about the internal fighting in the Roman Catholic Church (between Fiamma of the Right and the Pope), from which the Pope had been hospitalized. The boatman stated that the vast amounts of magic used should've caused more damage and was confused by it. However, Laura noted that there was an ordinary street behind the Pope, meaning the outcome was obvious - the Pope used himself to prevent the destruction of that street. In that boat, Laura mentioned that the Pope was such a kind man, and with a tinge of loneliness in her voice, wondered if he was smiling now.

Trivia

 * In the light novel, the narrow boat which Laura Stuart was riding in was not a rowboat, but a miniature engine was attached to boat. In the anime and manga adaptation, it was changed to the gondolier rowing the boat with the oars.
 * In the Toaru universe, Little Venice is the junction of three canals, as opposed two canals in real life.