The barrier-free redesign and modernization of the Belderberg underpass for pedestrians and cyclists is a central section of the "City on the Rhine" design manual adopted to improve the connection between the city centre and the banks of the Rhine. Around two million euros will be invested in the modernization of the underpass by the Civil Engineering Office of the City of Bonn, 80 percent of which will be covered by the state of North Rhine-Westphalia. The construction work over a length of around 160 meters is expected to last until the end of 2026.

The ramp to the underpass will be extended by around 20 meters due to the barrier-free expansion. In Brüdergasse, concrete block paving with natural stone facing in anthracite and different stone formats will be used. Stainless steel strips are set into the surface at intervals to emphasize the paths to the Rhine. When using the steel strips, care is taken to ensure appropriate slip resistance.

As in numerous streets in the city center, the pavement connections to the existing buildings are maintained by a three-line small pavement band in red natural stone. The surrounding area will be enhanced with additional benches, garbage cans and bicycle stands.

On the Rhine side of the underpass, a new direct path will be developed across the green space. This will create a straight connection from the underpass to the street Am Boeselagerhof in front of the opera house and on to the Rhine. By straightening the path, it can be made barrier-free and with a gradient of no more than six percent. With a width of four meters, the access route is designed to be friendly. The verges and hollows will be laid out as herb lawns and insect-friendly plants will be sown.

The underpass will be renovated and the damaged tiled wall cladding will be replaced with large-format Formica panels in grey. The ceiling will be recoated in white. All of the lighting will be replaced as part of the refurbishment to save energy.