The Dublin Port Tunnel is the largest civil engineering project in Ireland; only the Ardnacrusha hydro-electric scheme on the River Shannon comes close.
The project employed 5,000 people over the course of its construction, delivering eight million man-hours without incurring a single fatality.
Two million tonnes of rock and clay were moved over the five-year course of the project, yet the M1 was kept open throughout.
The construction site at Whitehall had a hole 56 metres in diameter, longer than an Olympic-size swimming pool and equivalent to seven storeys deep.
Much of the tunnel is 22 metres below ground; it was cut through hard limestone and boulder clay by two tunnel-boring machines named Gráinne and Megan.
During construction, Fairview Park had an excavation the size of a cathedral, which is currently being reinstated.
... The project involved 4,500 metres of boundary walls, either stone-clad or fitted with acoustic panels, as well as planting 40,000 trees and shrubs.
... The ventilation system is run by 16 jet fans which can change the air within minutes. The tunnel is also fitted with gas and fire detection equipment.