Up to 10,000 runners will make history today by taking part in the first Dublin Port Tunnel 10km Race.
Competitors in the landmark 6.2 mile event will run under the streets of the capital through one side of the twin tunnel, from the docks towards the M1, returning on the opposite side.
The wheelchair race starts at 10.45am with the rest of the runners following at 11am.
The winner is expected to cross the finish line at East Wall Road shortly after 11.30am.
The run is being held to mark the opening of the tunne, which will carry traffic from December 20.
The project is the largest ever civil engineering scheme ever carried out in the state, taking more than four and a half years to complete.
It is believed the 4.5km tunnels will carry thousands of heavy goods vehicles from Dublin Port on to the national roads network in six minutes.