This is one proposed design for the LHC tunnel at CERN. Though the LHC
will share the tunnel with the older LEP,
they are at present completely separate. One day physicists
may collide electrons from the LEP with protons from the LHC.
One of the four LEP monorail trains suspended from the ceiling of the 27 km
long LEP tunnel.
Three such trains circulate in the tunnel transporting goods
and people.
Computer graphics of LHC positioned in the existing LEP tunnel.