A final design is yet to be decided by the European organisation. The brief for the Project Office Einstein Telescope in this Euroregion involves a triangular-shaped tunnel with arms of (3 times) 10 kilometres long. It is an underground observatory that will be located at a depth of 250 to 300 metres. There will be underground rooms/chambers at the three vertices. Laser beams will run through the 10-kilometre arms (the tunnel tubes). A laser beam is split into two beams and these are reflected by mirrors at the ends of the arms in the underground chambers. From the three vertices, a lift will reach ground level. Maintenance will be carried out inside the tunnel via these shafts.