We carried out the structural design, civil works and foundation contract for a GIS substation built in a rock cavern. Building in a confined space required precise planning at every work stage. Our contract included all the steel and concrete structures of the GIS substation and their design, including base slabs, vaults, steel frames, and canopies. Sähkölandia Oy acted as the main contractor for the substation. The station was built for Naantalin Energia Oy.