Riga - capital of Latvia, the largest of the cities of the Baltic States, along with Vilnius iTallinom famous charm of this old Europe. From Kaliningrad region Riga separated 350 kilometers - a distance ridiculous for the traveler, and only for kubanoida - and at a trifling matter! Especially if you have a passport in your pocket with mnogokratnoyshengenskoy visa.
As to any other European cities to Riga can be reached in several ways: by plane, train, bus or car. You can choose a convenient option for you, depending on what city in Russia (or another country) you live, how quickly you want to get and at what cost. Passport with a Schengen visa, you will need anyway.