The lower chapel of the North tower is dedicated to St Peter and is 75 cm below the floor level of the west transept and the rest of the cathedral.
It was probably home to the treasury chamber from the fourteenth century.
For this reason, the access from the west transept was only through two doors – the south door led through a short passage to the chapel itself, while the north door led to the treasury chamber which was probably inside the masonry of the walls.

From the fifteenth century, the North tower was also the Armarium, the storage space for the holy scriptures.
It retained this function until 1 March 1859, when the cathedral chapter ordered the construction of a dividing wall between the chapel and the transept.
From 21 November 1793 until 27 March 1794, the tower held not only the cathedral treasury, but also Cologne cathedral treasury, which was brought to Münster for protection from the French during the War of the First Coalition.

After a decision on 21 December 1870, the baptismal font was moved into the Petruskapelle.
Along with this, it was closed off with the Landsberg iron grills, which had previously separated off the organ within the Old Choir.

A special feature of the tower is found high up in the upper chapel.
In a small chamber, there is a 0.8 m high and 1.4 m wide gravestone showing a woman in prayer.
It was apparently already old before the construction of the Westwerk in 1190, since there was no hesitation at recycling it as building material for the cathedral.

The North tower was badly damaged in the Second World War; the upper two levels were partially destroyed.
During the restoration, the aforementioned levels and the roof were rebuilt.
At the same time, the interior of the tower was renovated and the Petruskapelle made into the treasury chamber once more.
After the completion of the new treasury chamber to the north of the cloisters in 1981, the treasury was moved there.

In the "upper" chapel are the auxiliary works of the main organ.
The lower chapel of the North tower is dedicated to St Peter and is 75 cm below the floor level of the west transept and the rest of the cathedral. It was probably home to the treasury chamber from the fourteenth century. For this reason, the access from the west transept was only through two doors – the south door led through a short passage to the chapel itself, while the north door led to the treasury chamber which was probably inside the masonry of the walls.
From the fifteenth century, the North tower was also the Armarium, the storage space for the holy scriptures. It retained this function until 1 March 1859, when the cathedral chapter ordered the construction of a dividing wall between the chapel and the transept. From 21 November 1793 until 27 March 1794, the tower held not only the cathedral treasury, but also Cologne cathedral treasury, which was brought to Münster for protection from the French during the War of the First Coalition.
After a decision on 21 December 1870, the baptismal font was moved into the Petruskapelle. Along with this, it was closed off with the Landsberg iron grills, which had previously separated off the organ within the Old Choir.
A special feature of the tower is found high up in the upper chapel. In a small chamber, there is a 0.8 m high and 1.4 m wide gravestone showing a woman in prayer. It was apparently already old before the construction of the Westwerk in 1190, since there was no hesitation at recycling it as building material for the cathedral.
The North tower was badly damaged in the Second World War; the upper two levels were partially destroyed. During the restoration, the aforementioned levels and the roof were rebuilt. At the same time, the interior of the tower was renovated and the Petruskapelle made into the treasury chamber once more. After the completion of the new treasury chamber to the north of the cloisters in 1981, the treasury was moved there.
In the "upper" chapel are the auxiliary works of the main organ.
Münster Cathedral