The Baltic Sea was formed 15 thousand years ago when the glaciers of the last Ice Age melted. Compared with the world's oceans, it contains very little salt so its surface freezes in winter.

In summer, Baltic nights shrink to a few twilight hours. The sea's northern arm, the Gulf of Bothnia, almost reaches the Arctic Circle. Its eastern arm, the Gulf of Finland, stretches into Russia.Highslide JS

Nine countries have Baltic coastline, as the map shows. Because of shared history, Norway is sometimes included although its coast is all on the Atlantic. There are a dozen large Baltic islands and many thousands of smaller ones.

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The sea is long but thin, on average only about 190 km (120 miles) wide. In fact the name Baltic probably comes from the word balteus, the Latin for "belt".Highslide JS

Once it was crossed by Viking longboats and later by the ships of the Hanseatic League. Today its cities are connected by ferries and visited each summer by the world's leading cruise lines.

Discover the Baltic is designed to help visitors plan their days ashore in Helsinki, St Petersburg and Tallinn, with an honest and up-to-date descriptions of the cities and their sights.

At each port it tells you which harbour your ship will use. If it's on the outskirts of town, we show how to reach the centre, by shuttle bus, public transport, taxi or on foot.Highslide JS

At some ports all the main attractions are close together. At others, you'll need to do a bit of planning.

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