This feat of modern-day engineering burrows seven storeys beneath Dublin city, making your North South journey all that more swift and, dare we say, futuristic.

Opened on March 5, 2007, the 4.5km Tunnel is the largest ever roads transportation project in Ireland. Two 'one-way' tubes connect Dublin Port to the M1 and the National Roads network via the M50 at Coolock.

Tolls (€3-€10 each way depending on day and time) can be paid to a cashier, at a coin machine or in advance at www.etrip.ie. Commercial vehicles above 3.5 tonnes laden weight, buses wih 25+ seats and vehicles specially adapted for, and driven by, physically disabled drivers can travel toll-free. L-drivers, passengers and cyclists are restricted from using the Tunnel.

Access is 24/7 (except for occasional off-peak maintence closures - check in advance) and emergency telephones to the Tunnel Operator are at 250m intervals. Before entering remove sunglasses, turn on dipped headlights, check you've enough fuel and tune into any FM radio station for 'break-in' instructions from the Operator.