In the Early Iron Age, on the edge of the Vistula valley, a fortified settlement of the Lusatian culture was built. Long after its abandonment or destruction, in the 11th / 13th century, on the elevation left by the previous inhabitants, an extensive settlement complex was created, including a stronghold, a craftsmanship and trade settlement and two cemeteries. The complex in Kałdus was, next to Gdańsk, the most important settlement center in Eastern Pomerania in the early Middle Ages. Its strategic and political importance was determined by its convenient location at the intersection of the two main trade routes: the Vistula and the Ruthenian-Baltic routes. In the first half of the 11th century, there was a political center of Bolesław Chrobry and Mieszko II, at which the construction of a stone basilica also began. The function of the great sacral complex, founded on the periphery of the early Piast state, remains a mystery. The basilica was not completed, walls were raised to a height of about 1 meter, after which the construction was abandoned, probably due to the pagan reaction after 1034. The final end of the hillfort took place in the 20s of the 13th century, when the Prussians captured it and burnt it. The Teutonic watchtower, which was established in the 40’s of the 13th century, was quickly demolished.
The stronghold was situated near the eastern bank of the Vistula River. The hillfort rampart had a kidney shape with dimensions at the base: length from the inner 100 meters, from the outer 140 meters, the width at the base of 50 meters, and the height from the east side 15 meters.
A stone basilica, orientated to the east-west line, was erected directly at the base of the hillfort. The walls of this church, preserved in some places up to a meter high, were built of unworked stone in the opus emplectum technique, bound with lime mortar. They were about 1.95 meters thick. The exceptionally large dimensions of the building, about 36-37 meters long and about 17 meters wide, can only be compared with the size of the cathedral churches existing at that time in Gniezno and Poznań. It had three aisles, three apses, including two side ones and one main, protruding towards the east, and a small annex (4.3.5 meters) at the southern aisle, ended with a semicircular apse on the west side. Perhaps this annex served a baptismal function. Probably the basilica was never completed, because no traces of the internal divisions of the building, foundations of the pillars, remains of floors and architectural details have been found.
At present, the hill is protected as a steppe vegetation reserve St. Lawrence Mountain. There are no relics of buildings preserved on it, but the hillfort itself is legible.
Chudziak W., Geneza wczesnoromańskiej bazyliki z Kałdusa na Pomorzu Nadwiślańskim [w:] Początki architektury monumentalnej w Polsce, red. Janiak T., Stryniak D., Gniezno 2004.
Rodzińska-Chorąży T., Kilka uwag w sprawie metody prezentacji i interpretacji reliktów budowli sakralnej w Kałdusie, “Czaspismo techniczne”, zeszyt 23, rok 108, 2011.
Webpage odznaka.kuj-pom.bydgoszcz.pttk.pl, Góra św. Wawrzyńca W Kałdusie.