The Meeting at the tomb of Saint Adalbert is one of the most important events in Polish history, though scholars disagree over the details of the decisions made at the meeting, especially whether Polish prince was pledged the kings crown or not.
(See life of Adalbert of Prague).
After his death, Adalbert was soon made a saint by the common effort of Boleslaus I and Otto III, becoming the first saint of Slavic origins. His body, bought by Boleslaus I for its weight in gold, was put into the tomb in Gniezno, contemporary capital of Poland.
Otto III committed to a pilgrimage to Poland in his attempt to extend influence of Christianity in the eastern Europe. As part of this policy, he also invested Saint-King Stephen the Great of Hungary with the kings' crown.
While on a pilgrimage to the tomb of Saint Adalbert at Gniezno in 1000 A.D., Otto III, Emperor of the Holy Roman Empire, invested Boleslaus I of Poland with the title Frater et Cooperator Imperii ("Brother and Partner of the Empire").
On the same visit Otto III raised Gniezno to the rank of an archbishopric. Poland become separate from the bishopric of Magdeburg province of the church, which helped her to keep semi-independence from the Holy Roman Empire throught the Middle Ages. Eventually, Poland stayed outside the Holy Roman Empire, while e.g. Bohemia become one of its countries.
The event is described by German chronicle writer Thietmar and Polish Gall Anonymous.
See also: History of Poland