The tower known as a bergfried which is a type of medieval freestanding defensive tower. The lower inner part of the tower was vaulted, usually intended for a prison and only available from the top. The entrance to the tower was originally placed quite high, only accessible by a wooden footbridge from neighbouring defensive walls that no longer exist.

Its position and surviving Gothic features really shows the medieval character of the castle; a Gothic doorway survives on the southern side of the tower, and its position suggests that the original entrance may have been reached from the wall walk of the medieval fortifications. However, the tower's original appearance is not known with certainty. One possibility proposed by recent research is that it may once have had a masonry roof or “helmet”, this can be found on a similar tower in Kokořín Castle, which could have been removed when the tower was later converted into a bell tower. This remains a hypothesis rather than an established reconstruction.

Source: Josefina Jadnáková's 2024–2025 architectural/heritage study, Obnova předzámčí v Ratajích nad Sázavou

In 1447, one of the Rataje castles was reportedly damaged by fire, attributed to the carelessness of servants. The surviving source does not make clear whether this refers to the Upper Castle or Pirkštejn, although it notes that the administrative centre of the estate was located at Pirkštejn at the time.

Source: Pamatky.cz, ‘Rataje nad Sázavou – Zámek’, updated 24 August 2026. Pamatky.cz – Rataje nad Sázavou

From approximately the first half of the 16th century, Pirkštejn was abandoned as a residence. The upper castle became the principal seat, while the lower castle was left neglected and without a residential function.

A major change came in the early 18th century. Between approximately 1713 and 1724, the abandoned castle was converted into a parish house. As part of these works, the original defensive bergfried was transformed into a bell tower. Its upper floors were demolished, while the surviving second floor was raised with new masonry. A wooden superstructure containing two bells was then installed above it. The bells were probably transferred from the town's former Gothic church.

Today the medieval defensive structure remains, but the upper portion was altered to serve a religious purpose. Its surviving Gothic masonry preserves part of Pirkštejn's medieval defensive history, while its wooden bell-tower structure records the building's transformation into a parish complex in the 18th century.