The former main post office building is located in the centre of Basel, directly above the underground Birsig Canal. Originally built as a department store in the 14th century, it housed the post office from the 19th century onwards. The building ensemble consists of different parts from various eras. While the exterior appearance has been largely preserved, numerous structural changes have been made to the interior over the decades. Parts of the complex, such as the sandstone façade and the counter hall on the ground floor with its slender, neo-Gothic cast-iron columns and wall paintings, have been listed as historical monuments since 2002.

The renovation was carried out in accordance with historical preservation guidelines and careful analyses of the existing structure. Later additions and alterations were removed to expose the original structures. The supporting structure was analysed step by step. Due to a lack of existing documentation for some areas, the condition of many components had to be examined and documented directly on site.

The structural assessment was carried out by systematically recording the existing components and testing their load-bearing capacity and serviceability in accordance with current standards. A key issue was earthquake reinforcement, which was implemented across the entire height of the building from the second basement to the fourth floor. Particular challenges also arose due to the limited space available in the inner city and the old underground Birsig canal, which is centuries old.