Budapest is the capital of Hungary. As the largest city of Hungary, it serves as the country's principal political, cultural, commercial, industrial, and transportation centre. In 2010, Budapest had 1,721,556 inhabitants, down from its 1980 peak of 2.06 million. The Budapest Commuter Area is home to 3,271,110 people. The city covers an area of 525 square kilometres (202.7 sq mi) within the city limits. Budapest became a single city occupying both banks of the river Danube with a unification on 17 November 1873 of right (west)-bank Buda and Óbuda with left (east)-bank Pest. Budapest is one of Europe's most delightful and enjoyable cities. Due to its scenic setting and its architecture it is nicknamed "Paris of the East".

Bucharest is the capital city, cultural, industrial, and financial centre of Romania. It is the largest city in Romania and was first mentioned in documents as early as 1459. Since then it has gone through a variety of changes, becoming the state capital of Romania in 1862 and steadily consolidating its position as the centre of the Romanian mass media, culture and arts. Its eclectic architecture is a mix of historical, interbellum, Communist-era and modern. In the period between the two World Wars, the city's elegant architecture and the sophistication of its elite earned Bucharest the nickname of the "Little Paris of the East".

Istanbul, historically known as Byzantium and Constantinople is the largest city in Turkey and 5th largest city proper in the world with a population of 13 million, also making it the largest metropolitan city proper in Europe and the second largest metropolitan area in Europe by population. Istanbul is also a megacity, as well as the cultural, economic, and financial centre of Turkey. The city covers 39 districts of the Istanbul province. It is located on the Bosphorus Strait and encompasses the natural harbour known as the Golden Horn, in the northwest of the country. It extends both on the European Thrace and on the Asian Anatolia sides of the Bosphorus, and is thereby the only metropolis in the world that is situated on two continents. Istanbul is a designated alpha world city.

Belgrade is the capital and largest city of Serbia. The city lies at the confluence of the Sava and Danube rivers, where the Pannonian Plain meets the Balkans. It has an urban population of 1.2 million, while the metropolitan area has more than 1.7 million people, making it one of the largest cities of Southeastern Europe. Its name translates to white city. Belgrade's wider city area was the birthplace of the largest prehistoric culture of Europe, the Vinča culture, as early as the 6th millennium BC. In antiquity, the area of Belgrade was inhabited by a Thraco-Dacian tribe Singi, while after 279 BC a Celtic tribe inhabited the city, naming it "Singidun".