Bohemia's borders are marked with mountain ranges such as the Ĺ umava, the Ore Mountains or Giant Mountains as part of the Sudeten mountains.
With Bohemia's conversion to Christianity in the 9th century, close relations were forged with the East Frankish kingdom, then part of the so-called Carolingian empire, later the nucleus of the Holy Roman Empire of which Bohemia was an autonomous part from the 10th century.
During the ecunemical Council of Constance in summer of 1415, the rector of the University of Prague and prominent reformer and religious thinker Jan Hus was sentenced to be burnt at the stake as a heretic.