Trains are now running between Newquay and Par in Cornwall after Network Rail completed emergency repairs.
Engineers had been working for two weeks to rebuild a retaining wall on an embankment near Pontsmill viaduct.
The wall had fallen into the river below the railway line and displaced a significant amount of ballast.
Chris Fuoco, Network Rail’s director for Devon and Cornwall, said: “We thank passengers for their patience while we completed the urgent repairs on the line between Par and Newquay.
“We worked as quickly as possible to repair the railway and ensure your journeys remain safe.”
The repairs were not related to engineering work on the Mid Cornwall Metro project.
The scheme, which is scheduled for completion in 2026, will create a direct rail link between Newquay and Falmouth.