Mechelen is an underrated town. It is located south of Antwerp, just about 20 minutes away by train. It has a pretty Old Town, and it has a few interesting museums, plus a church with a very tall belfry. And based on what I have heard, it is also the religious heart of Belgium.
The Old Town is a typical Flemish one, with a Grote Markt, and the Town Hall on the center of it. There are plenty of thin houses lining the streets. And there are also canals, though not as pretty as the ones in Bruges.
The canals however have some walkway where you can actually enter, so that you're walking right by the water, instead of by the roadside. This was an interesting way to discover the city.
They say that Mechelen is a religious place, but to be honest, aside from the numerous churches, I didn't really found that palpable. Rather, I thought it was a city that had plenty to do, especially if all you have is a day. I checked out an interesting historical museum, and I also entered a free art gallery (more about these later). So if you only have a day to visit, then Mechelen is the right size so to speak.