The excavations in the 1970s showed that the Castle walls are made of large, partially hewn boulders that are laid in horizontal, precisely marked rows. The stones are well matched end-to-end. The gaps between them are filled with stone fragments on lime mortar, a solidified fragment of which you can see in this showcase.
Brick was used only for basic structural elements and architectural details. The corners of the Castle walls and towers, decorative belts on the facades of the eastern and northern walls, arches, vaults, loopholes and the outer surfaces of the parapet of the fighting gallery (krenelering) are made of brick.
You can see the craftsman's fingerprints on the brick. It is because of such fingerprints, the brick was named “brick with longitudinal grooves from the fingers”. Such grooves left by the craftsman increased the area of adhesion of the brick to the mortar and, as a result, provided a stronger masonry. Both towers were covered with semicircular roofing tiles.