Take a boat to tour on the marshes and alligator-free swamps surrounding Saint-Omer.
The Luminarc glassware factory can be visited in the vicinity. 8th biggest industrial site in France, it produces 4 million items every day.
WW2 Museum with one of the only V2 rocket launching bunker.
Try to see the UK from across the Channel standing from the top of a chalk cliff
Go visit the fortified city of Bergues. Typical place mixing Flanders style and Vauban fortifications.