The Baltic languages are a subbranch of the Balto-Slavic branch of the Indo-European language family spoken by the Balts. Baltic languages are spoken mainly in areas extending east and southeast of the Baltic Sea in Northern Europe. The group is usually divided into two sub-groups: Western Baltic, containing only extinct languages, and Eastern Baltic, containing both extinct and the two living languages in the group: Lithuanian (including both Standard Lithuanian and Samogitian) and Latvian (including both literary Latvian and Latgalian). The range of Eastern Balts reached to the Ural mountains. While related, the Lithuanian, the Latvian, and particularly the Old Prussian vocabularies differ substantially from one another and are not mutually intelligible. The now-extinct Old Prussian language has been considered the most archaic of the Baltic languages.