Palazzo Contarini di Bovolo
Designed and built by Giovanni Candi in 1499, Giorgio Spavento later designed the famous spiral staircase located on the facade of the palace.
There are two stories about how and why the staircase was built: the first is that the owners of the palazzo, the Contarini family, left for vacation and simply gave the instructions to "build me a staircase" (Spavento might have been a bit of an overachiever). The second was that the staircase was built on the outside of the palace because towers were not permitted to be built in the city at the time of the construction of the main building. (Venice is built on the water so the poor bearing capacity of the soil leads to earthquakes, collapses and demolitions).
The original building was curious but not prestigious, tucked away in an obscure alley near the Piazza San Marco. After the wall protecting the small courtyard was brought down, Spavento was commissioned to create the staircase, which he did, using the model of the Byzantine scalar towers as inspiration. A series of overlapping loggias connect the floors to the airy staircase. The palace takes after a few different types of architecture and design. There are Renaissance, Byzantine and Gothic styles incorporated in and outside the building.
The name of the building: Contarini del Bovolo. Contarini was the name of the owners and "bovolo" means snail shell in the Venetian dialect. Sometimes the palace is simply referred to as the "snail house".
Around the base of the palazzo are numerous wellheads or "vere di pozzo". Most are much older than the building itself, dating back to the 13th century, and were incorporated into the structure. A few were made after the construction of the building though because they have the coat of arms of the family on them.
In 1949 the English director Orson Welles began filming a famous literary classic: Othello by William Shakespeare, whose first act was set in Venice. Throughout the movie, the famous spiral staircase was put on display many times.
As of 2016 (after some renovations) the staircase is accessible to the public for a small fee.
https://web.archive.org/web/20111130111531/http://www.euro-poi.com/venice-bovolo-house-italy-383.html
https://web.archive.org/web/20060507133401/http://www.scalabovolo.org/bovolo2.html
https://web.archive.org/web/20110929112453/http://www.venice-sights.co.uk/Contarini_del_Bovolo.htm
https://www.visitvenezia.eu/en/venetianity/discover-venice/venice-and-its-%E2%80%98caskets--the-bell-towers-
https://www.venetoinside.com/hidden-treasures/post/the-othello-by-orson-welles-and-the-bovolo-stairs-in-venice/