Changes during the Latin Empire
"It was also, with reasonable certainty, the Latins who, finding no church bells in Hagia Sophia, erected a belfry supported by buttress-piers in the center of the west façade. That high rectangular tower has vanished, but according to eyewitness
Richard Winston. Hagia Sophia, A History (Locais do Kindle 950-952). New Word City, Inc.. Edição do Kindle.