Where in the world?
The flag of Gibraltar has a white field with a red stripe at the bottom and a red castle in the center.

Gibraltar

Population: 33,691

Region: Europe

Subregion: Southern Europe

Capital: Gibraltar

Top Level Domain: .gi

Currencies: Gibraltar pound

Border countries

The flag of Spain has three horizontal stripes of red, yellow, and red with the national coat of arms on the yellow stripe.

Spain

Population: 47,351,567

Region: Europe

Capital: Madrid