Where in the world?
The flag of Bulgaria has three horizontal stripes of white, green, and red.

Bulgaria

България

Population: 6,927,288

Region: Europe

Subregion: Eastern Europe

Capital: Sofia

Top Level Domain: .bg

Currencies: Bulgarian lev

Border countries

The flag of Greece has nine horizontal stripes of blue and white, with a blue canton containing a white cross.

Greece

Population: 10,715,549

Region: Europe

Capital: Athens
The flag of North Macedonia has a red field with a yellow sun in the center, featuring eight broadening rays extending to the edges of the field.

North Macedonia

Population: 2,083,380

Region: Europe

Capital: Skopje
The flag of Romania has three vertical stripes of blue, yellow, and red.

Romania

Population: 19,286,123

Region: Europe

Capital: Bucharest
The flag of Serbia has a red, blue, and white horizontal tricolor with a coat of arms on the left side.

Serbia

Population: 6,908,224

Region: Europe

Capital: Belgrade
The flag of Turkey has a red field with a white star and crescent slightly left of center.

Turkey

Population: 84,339,067

Region: Asia

Capital: Ankara