A must see
Voetgangerstunnel (pedestrians' tunnel)21
Why locals love it
The pedestrian's tunnel connects the more quiet, peaceful left bank ("Linkeroever") and the more exciting, crowded right bank ("Rechteroever") of Antwerpen. But it's not only of practical use, but it's also a special place to visit since the tunnel with its escalators is quite old and has its own feel to it.
Why you should visit it
First, you should look around when you're walking through the tunnel. Admire the sights and inhale the atmosphere. Second, when you're on the Left Bank, you can get a break from the city bustle and have a quiet picnic, or a lovely walk.
There is a lift as well, but this is (so I have heard) quite often out of use...