In 1285, Tallinn, then known more widely as Reval, became the northernmost member of the Hanseatic League – a mercantile and military alliance of German-dominated cities in Northern Europe. The king of Denmark sold Reval along with other land possessions in northern Estonia to the Teutonic Knights in 1346. Medieval Reval enjoyed a strategic position at the crossroads of trade between Western and Northern Europe and Russia. The city, with a population of about 8,000, was very well fortified with city walls and 66 defence towers.