Although the Chunnel is a rail tunnel, rather than a highway tunnel, I thought the portals deserved some attention.
First, the French portal:
and, across the English Channel, the English portal:
The Chunnel is the world’s longest undersea rail tunnel. Opened in 1995, it provides a rail link between England and mainland Europe. The two terminals shown in maps above provide facilities for passenger vehicles and cargo trucks to board and disembark shuttle trains to quickly cross traverse the English Channel.