For the purpose of preparing technical documentation for the rehabilitation of tunnels within the Belgrade Railway Junction, the Institute of Transportation CIP is conducting geotechnical investigations to assess the condition of the Vračar, Dedinje, Stadion, and Vezni tunnels. During the periodic suspension of traffic and disconnection of the overhead catenary system at night, specially trained CIPTeam representatives perform detailed visual inspections of the tunnels, exploratory drilling of the tunnel lining and the rock mass behind the lining, as well as the invert arch and the ground beneath the invert arch, with sampling of concrete, soil and rocks for laboratory tests. The obtained results will be the basis for the continuation of design work.