Stuttgart 21 is a £9bn railway redevelopment in Stuttgart, Germany, featuring new stations, tunnels, and bridges. Set to open in 2026 after years of delays, it aims to improve high-speed rail connections across Europe, drastically reducing travel times and integrating Stuttgart Airport into the long-distance rail network, enhancing regional and international connectivity.

Source:  https://www.express.co.uk/news/world/1958455/Stuttgart-21-Europe-railway-network