I'm going to travel by car from Netherlands to Luxemburg. Whole round-trip starts from the Baltics - Germany - Netherlands - Belgum - Luxemburg - towards Baltics. I'm not in a hurry and I would like to spend some time sightseeing.
I'm not looking for "just beautiful" buildings, famous statues, amusement parks or similar places where one could spend their all day and all their money.
Some examples from another countries I liked: Hill of crosses in Lithuania, Wieliczka(in Poland) salt mine, windmills in Netherlands, some great Castles - things that make you go "wow" one way or another
What are a must-see places in Belgium?