By Spring 2001, work on the stone structure had progressed to such an extent that the geometrical separation of the individual building parts was clearly visible from the scaffolding level below the canopy: The inner dome above the church room separates from the stonework ring that will carry the main dome and rises towards the upper compression ring. The stonework ring, on the other hand, rises vertically and will form the outer façade with the first layer of the tambour cornice ring at a height of 37.5 m. Alongside this the staircase towers rise to the heavens like spires, the only difference being there are four of them.  After months of working in two shifts, the last stone of the upper compression ring could be placed on 29th July 2001. The inner dome with its circular 6 m opening was thereby completed as the connection between church room and main dome room. This beautiful part of the building is a perfect piece of sandstone work and separates into load-bearing ribs and intermediate stonework in the upper section, which unfortunately will not be visible later on. The underside will be plastered and the top will be covered by an inserted ceiling. All that will remain visible are the ashlars of the upper and lower compression ring.   It took a lot of technical finesse to return the ‘butterfly’ to its original place. This big compound of original stones had been lying on the north side since the beginning of the rebuilding process, rotated by 180° just as it had been on the mound of rubble. The curved projections of the staircase spire made it look like a butterfly. After restoration, this big part 35 was lifted on top of the staircase tower G on 10th August 2001.   The concave dome batter also posed a few problems. It gives the dome its unique bell shape and is thus the point where the geometrical form of the square changes into a circle. This section had suffered repeated damage due to penetrating rain water. The penetrating water thus had to be diverted into ducts covered by plates on the main cornice in future. The cover plates of the dome batter thus had to be laid on masonry dowels. A spray seal was applied before assembly that channels off any water that penetrates through the cover plates.