The body of the 20-30-year-old was discovered about 6am near the base of the Kings Avenue bridge. A Queanbeyan Elite taxi station wagon was found unlocked and abandoned on the northern end of the bridge.

Police sealed off all north-bound traffic and one south-bound lane for much of the day, creating havoc for both cars and pedestrians on one of Canberra's busiest north-south accesses.

An ACT Policing spokesman said the body had been sent for forensic testing and the death was being treated as suspicious. Anyone with information should contact Crime Stoppers on 1800 333 000.