Odesa is the third most populous city and municipality in Ukraine and a major seaport and transport hub located in the south-west of the country, on the northwestern shore of the Black Sea. The city is also the administrative centre of the Odesa Raion and Odesa Oblast, as well as a multiethnic cultural centre. As of January 2021, Odesa's population was approximately 1,010,537. On 25 January 2023, its historic city centre was declared a World Heritage Site and added to the List of World Heritage in Danger by the UNESCO World Heritage Committee in recognition of its influence on cinema, literature, and the arts. The declaration was made in response to the bombing of Odesa during the Russian invasion of Ukraine, which has damaged or destroyed buildings across the city.

Saint Petersburg, formerly known as Petrograd and later Leningrad, is the second-largest city in Russia after Moscow. It is situated on the River Neva, at the head of the Gulf of Finland on the Baltic Sea. The city had a population of roughly 5.6 million residents as of 2021, with more than 6.4 million people living in the metropolitan area. Saint Petersburg is the fourth-most populous city in Europe, the most populous city on the Baltic Sea, and the world's northernmost city of more than 1 million residents. As Russia's Imperial capital, and a historically strategic port, it is governed as a federal city.