Yes, infrastructure wise, Channel Tunnel is Europe's biggest projects ever. It is around 31 miles long and 150 feet deep under the seabed.

This Tunnel has around 3 tubes, 2 for rail and 1 for service, and 3 of them were dug by around 13,000 workers and engineers and it cost around 15 billion dollars to build up.

The Channel Tunnel is undoubtedly the fastest way of traveling between Paris/Brussels and London. You can also take single day trip to Paris and back if you wish.