Following the start of construction on August 27, 2025, the first of three construction phases was completed after about one year—approximately nine months ahead of schedule. This marks an important milestone for the overall project: 24 new trees were planted, new natural stone paving was laid, and the technical infrastructure for the square’s diverse uses was established.

“Schlossplatz is the heart and stage of our city. I am all the more pleased that it is available again well ahead of the originally scheduled date and just in time for the wine festival,” says Mayor Gert-Uwe Mende. “This is where tradition, social interaction, and downtown life come together. The redesign balances the needs of events with more shade, a pleasant atmosphere, and climate-adapted greenery. In this way, we’re preserving the square’s time-honored use while also making it ready for the future.”

“We’ve redesigned Schlossplatz so that the trees have good growing conditions despite the square’s heavy use,” says Andreas Kowol, head of the building department. “Of particular importance are the large underground tree compartments over which the paving ‘floats’ on a self-supporting substructure. Above ground, you can only see the tree pits, but beneath them, the roots have access to extensive, interconnected planting spaces. What’s happening here is an investment in the future: year after year, the tree canopies will expand and provide more and more shade.”

The redesign not only enhances the visual appeal of Schlossplatz but also makes it technically and ecologically sustainable for the future. The square in the historic center sees heavy use every year—including for Wine Week, the Shooting Star Market, the International City Festival, and the Carnival Parade. In addition, it serves as an alternative venue when the Dern’sche grounds are occupied. For this reason, the redesign focused not only on an appealing appearance but, above all, on a robust, climate-adapted, and sustainable long-term solution.

Two large, contiguous underground tree quarters were created beneath the square, each accommodating twelve trees. Each of these compartments is about 1.5 meters deep and covers an area of approximately 9 by 30 meters. This provides significantly more space for the roots than is visible on the surface. This large underground root space is crucial for the long-term development of the trees.

The paving over the new tree sites rests on a steel beam substructure to prevent further soil compaction during festivals, temporary structures, and public traffic. The paving “floats,” so to speak, above the ground. This provides better protection for the trees and their root zones while still allowing the square to be used for events without permanently stressing the soil layers. This means that booths can be safely set up while the roots retain sufficient air and space.

The system is supplemented by two cisterns, each with a capacity of 20 cubic meters (for a total capacity of 40,000 liters), located between the Schweiger monument and the Marktkirche. Rainwater from the entire square is collected there and used for the sustainable irrigation of the trees. In addition, the drainage system is designed so that water can also flow away through the tree locations. The electricity, water, and wastewater connections for the stall operators are already buried underground and can be raised as needed. This makes the square accessible during events, as there are no loose cables, cable bridges, or other tripping hazards.

Japanese ornamental cherry (Prunus serrulata ‘Kanzan’), white mulberry (Morus alba ‘Fruitless’), and tulip tree (Liriodendron tulipifera) have been planted. The species were selected to suit the location and are adapted to dry, hot conditions. Over the long term, they are expected to develop into healthy, shade-providing, and climate-resilient trees that will improve the urban climate.

The Japanese ornamental cherry produces striking blossoms in the spring; the white mulberry is robust, heat-tolerant, and well-suited as a street and urban tree; and the tulip tree develops a large canopy with high shade potential. Together, the trees are expected to enhance the quality of the space in the future and make Schlossplatz more usable even on hot days.

Incidentally, the level of surface sealing on the square has not increased compared to before: a different type of paving material was simply installed that is better suited to future use. The new natural stone paving currently appears “more solid” because the trees are still young; as their canopies grow, they will provide more shade and create a more open, airy appearance.

Work on the future green space to the left in front of the church is still pending. Archaeological surveys and a search for potential unexploded ordnance will be conducted there first, as the area may be contaminated due to wartime activity. The footpath to the daycare center will be completed after the Rheingau Wine Week. 

As part of the redesign of the entire site, this green space will be relocated about ten meters to the north and upgraded. To protect the planting areas from disruption and damage caused by events in the future, the area will be enclosed and replanted. As a result, event booths will no longer be able to be set up there, eliminating the need for costly restoration measures. This will allow the area to fulfill its role as green space year-round. Aspects such as heat protection, climate resilience, and shade play a key role in the planning of the green space, which is still in progress. 

The significant reduction in construction time is the result of optimized construction scheduling, the dedicated and efficient execution by the contracted construction company, and the excellent collaboration among all partners involved in the project. Other positive factors included more favorable ground conditions than originally anticipated, as well as the swift completion and approval of the archaeological investigations. 

“The fact that this construction phase was completed so early demonstrates what can be achieved through good planning, trusting collaboration, and the high level of commitment from everyone involved in the project. Our special thanks go to the employees of the participating companies, the planning firms, and the relevant authorities,” stated Mayor Mende and City Councilor Kowol. “We would also like to thank all citizens, business owners, church congregations, and visitors to the downtown area for their understanding and patience during the construction period.”

The total cost of the first construction phase amounts to approximately 4.5 million euros. As things stand, the planned budget is being fully adhered to.

Once the city committees have approved the plans for the subsequent construction phases, the redesign of Schlossplatz will continue step by step to create a modern and multifunctional urban space. The state capital will continue to keep the public regularly informed about the project’s progress during the remaining construction phases.

With this redesign, the city aims to preserve Schlossplatz as an important event venue with a high-performance technical infrastructure while simultaneously developing it to be climate-resilient. In general, the city of Wiesbaden strives to remove impervious surfaces and introduce greenery in inner-city areas wherever possible. Current examples include Elsässer Platz and Bülowplätzchen in the Westend district, the planned tree plantings on Schwalbacher Straße, and, in addition, the “500-Tree Program.”