The Russian Enclave if Kaliningrad (amongst others)
Stockholm
Copenhagen
The Baltic is a sea and not a country
The country that is south of Latvia and has a coastline on the Baltic Sea is Lithuania. Its capital is Vilnius.
Vilnius is the capital city of Lithuania, the country that is south of Latvia and has a coastline on the Baltic Sea.
denmark
The capital of the country that separates the North Sea from the Baltic Sea is Copenhagen, which is the capital of Denmark.
That is Vilnius, capital of Lithuania
The capital of Finland is Helsinki and it lies on an island surrounding water, which is the Gulf of Finland. The Gulf of Finland stretches out, into the Baltic Sea.
There is no such country and therefore no such capital. If perhaps you meant to ask about the Mediterranean and Black Seas, the answer would be Turkey. If perhaps you meant to ask about the Baltic and Black Seas, the answer is Russia.
Helsinki, the capital of Finland is on the Baltic Sea.
Gotland, administered by Sweden
The Baltic Sea.
The baltic sea!