Philadelphia

Columns: City | Country | Date
Florence | Italy | 1964 | Tel Aviv | Israel | 1966 | Toruń | Poland | 1976 | Tianjin | China | 1979 | Incheon | South Korea | 1984 | Douala | Cameroon | 1986 | Nizhny Novgorod | Russia | 1992 | Frankfurt | Germany | 2015

Example questions:
What powerful family ruled the city that became a sister city of Philadelphia in 1964 ? | Who is the mayor of the city that became sister city of Philadelphia in 1966 ? | In 1233 which knights expanded the city that became the sister city of Philadelphia in 1976 ? | Which gulf is to the east of the sister city of Philadelphia that is in China ?

Answers:
Medici | Ron Huldai | Teutonic Knights | Bohai Gulf