Lithuania, Latvia, and Estonia- the Baltic Nations- derive most foreign influence on their culture from their immediate neighbors (principally Russia, their post-war occupiers untill 1990), but did you know there's a direct, delicious link between their beer and that of England?
Beginning in the late 18th century, the porter breweries of England began searching for continental export markets. Since the North Sea and the Baltic provided a natural shipping route to the Scandinavian and Baltic countries. English porter soon found devotees in the aforementioned countries, as well as in Sweden, Finland, and Poland.
Around the same time, English breweries started exporting stout and porter to Czarist Russia. Because the voyage was long an cold, the beer was made extra strong. It soon found favor in all levels of Russian society, even in the Imperial court itself.
This "Imperial Stout" became a style in its own right, and countries along the shipping route began to adopt recipes for a mishmash of porter and strong stout. Today's Baltic porter is a style in its own right. Dark and complex, with caramel coloring and a mild but noticeble roasted flavor, Baltic porters are more interesting than their English cousins. For all their opacity and flavor, however, they're surprisingly light in body, reminiscent of a German Dunkel. They're also on the strong side at around 5.5%-7% abv.
I've never seen a Baltic porter in a bar. When beer shopping, look for Okocim Porter, (Poland), Aldaris (Latvia), and Saku (Estonia) among others.