Antwerp is one big city of Belgium. It is mostly known for being a Diamond dealing place. But its way more. It is easy to visit by foot or by bicycle – quite like most big cities in Belgium.
The first thing I would really advise is to join the city by train. The train station is a big place and quite diffrent from other train stations. The railways of the train station are superposed, meaning deployed horizontally and vertically. The railway decks are between the floors 1-4 where two of them are underground.
So you can take your train from the overground or underground. It is as well a wonder of architecture. Once you have step out of your train and reach the top floor, you will discover a beautiful window roof bringing natural light in the whole building.