Archaeological Museum, which is placed in eastern Lithuania. It is enough to mentioned that this outstanding museums is listed n the UNESCO list! There is also wonderful Kernave Archaeological Site, where you can see remains of the medieval town. For instance, if you like the modern history, you should unquestionably visit the Paneriai Memorial. That museum is dedicated to all victims of the Holocaust. Furthermore, there is also the KGB museum (also called the Museum of Genocide Victims). This museum is dedicated to the period under the Soviet rule as well as to repression against Lithuanian citizens.
In case to visit the second country, which is a paradise for history fans, you should take one of a lot of cheap flights to Russia. When you are there, you will have a chance to discover places and sites where many crucial historical events took place (http://www.lot.com/airline-tickets/flights-to-russia). For instance, if you visit St Petersburg, you could visit the Church of the Saviour on Blood, which was built on the place where Tsar Alexander II was killed in 1881.