With its cruciform ground-plan and five towers the Church of Our Lady is unique. It is Kalundborg's landmark and most striking relic of an epoch of greatness. The church is situated on a mound whose low western spur was fortified by the powerful nobleman Esbern Snare c. 1170 against attacks by Wendic pirates. "The high-town" on the hill above the harbour was enclosed by ring-walls and ditches in the 14th century, and a new stronghold was built to the east (Kalundborg Castle). All this disappeared after the Middle Ages, although a number of medieval brick-houses close to the church still bear testimony to the heyday of the town in the 15th century.

The churchyard's medieval walls are all intact, but the three gates are of more recent date. Two brick houses from c. 1500 form part of the boundary walls: the tithe barn (the parish hall since 1973-74) to the south-east; and the school and presbytery (the mortuary since 1877) to the north-west.

Today the Church of Our Lady is marked by restorations undertaken in 1867-71 and 1917-21. The nucleus of the ground-plan is a square nave, from which extend four arms of equal length, each with a polygonal terminal. The internal circumference, which seems to be based on 30,75 cm as unit of measurement, is proportionated according to simple numerical ratios corresponding to music's harmonic overtones. Apart from this reflection of the celestial Master-Builder's universal laws, it should be noted that the circumference of the nave amounts to 144 units, which corresponds to the description of Celestial Jerusalem (NT, Rev., 21,17). The building material is large medieval red bricks, augmented by granite, the strength and load capacity of which is demonstrated by the four great columns carrying the nave's central tower. The three entrances to the church, like the windows, are reconstructions from 1917-21. The interior of the church is like a delicate miniature compared with the lofty rubustness of its exterior. Walls are of exposed red brickwork but the whitewashed plaster of window splays, above doors, and of the vaults provide a bright contrast. A mural fragment c. 1225 in the north window of the chancel shows that the interior was once enriched by murals. The engaged columns in the nave, the stairs in the south-east corner, and the nine groin vaults are reconstuctions from 1917-21, whereas the barrel vaults of the transepts which partly bear the outer towers are original.
Scholarly research has been divided on the question of architectural prototypes (Byzantine, Russian wooden architechture, fortifications etc.). However, according to the latest evaluations, the church is above all an ambitious attempt to create a work of architechture steeped in symbols to bring to mind the biblical description of Celestial Jerusalem; in other words, a divine fortress in stone similar to other artistic prefigurations of the celestial dwellings (altars, censers, font covers etc.) whose meaning is often documented by inscription. In its material form the architechture reveals borrowings from local centralised palace-churches, copies of the Church of the Holy Sepulchre, as well as grouped towers in the great churches of France and the Rhineland. Whereas the technical solutions have been intimately linked with the early brick buildings erected in Zealand.

No medieval sources mention the name of the person who built the church, or give any date. In the Renaissance it was assigned to the same period as Esbern Snare's castle, c. 1170. But a reappraisal of its stylistic characteristics suggests a slightly later date - sometime during the early decades of the 13th century when Esbern Snare's daughter, Ingeborg owned the castle. The medieval sacristy, built c. 1400, abutting the north wall of the chancel is preserved, and c. 1500 it was given an upper storey. By about 1800 the church had fallen into a serious state of dilapidation, and a restoration carried out in 1820-22 did not prevent the central tower from collapsing in 1827. It was rebuilt 1867-71 in connection with the extensive restoration of the church which, however, had to be rectified on a large number of points fifty years later. Very little of the church's medieval furniture has survived. The granite font, carved by a stone mason who worked for other members of the Esbern Snare family, dates from the time the church was built. A small Romanesque crucifix of bronze may have been part of a so-called "golden altar". From the late medieval period dates a crucifix figure of wood, c. 1500, from the Rood altar, and two pairs of altar candlesticks. The Reformation's new order of service resulted in the relatively small interior becoming filled to the bursting point with pews and galleries; these were removed about 1820. The altar-piece was carved in 1650 by Lorentz Jørgensen of Holbæk (its polychromy dates from 1701), whereas the present pulpit was built to the design of Vilhelm Tvede in 1871, and embellished with contemporary paintings by Anton Dorph. The chairs and organ loft above the porch in the west transept were made in 1917-21, but the organ has been built in 1957 by Th. Frobenius & Co. The stained glass panes in the north transept are by Emmanuel Vigeland (1928). Three wall monuments from the 16th and 17th centuries are preserved inside the church, whereas a considerable number of tombstones, mostly 18th century, are now either in the churchyard or lined up in the mortuary.

Translated by Jean Olsen