The coronation of Birger Jarlsson Valdemar took place in the cathedral in 1251; and in the reign of Gustavus Vasa several important diets were held in the town.
At the two Diets held by him, at Kassa and Talya, in 1683, the estates, though not uninfluenced by his personal charm, showed some want of confidence in him, fearing lest he might sacrifice the national independence to the Turkish alliance.
In his episcopal capacity he attended several diets of the empire, as well as the opening meetings of the council of Trent; and the influence of his father, now chancellor, led to his being entrusted with many difficult and delicate pieces of public business, in the execution of which he developed a rare talent for diplomacy, and at the same time acquired an intimate acquaintance with most of the currents of European politics.
It was often the meeting-place of German diets, twenty-three of which are said to have been held here, and was frequently the residence of the emperors.
The united diet which was opened on the 3rd of February 1847 was no more than a congregation of the diets instituted by Frederick William III.