Just south of the Belgian/Netherlands border is a great place called the "Bakkersmolen", or as you might guess..."the baker's [wind]mill."
It has a working windmill [which the owner built], a steam locomotive [giving rides to children], a steam-powered carousel, bakery [using grain milled in the windmill], and many, many other interesting things.
We have friends in Belgium who took us there in September 2005. We saw no other 'foreign' visitors, and our friends told us that indeed it's really only Belgians or Dutch that even know about it. In fact, the only pages I have seen about it are written in Dutch.
There is no charge for admission, but they would like visitors if possible to patronize the [delicious] bakery, which isn't much to ask! They also serve food and beverages for reasonable prices...like the wonderful De Konnick beer. We were there during beautiful weather, and sat outside on the patio.
It's an impressive place, and if you like machinery or even just fresh bread, you cannot help to admire the vision and drive of the man who has built this place. It's quite a testament to his energy and enthusiasm.
Their web page is quite crude, but has a lot of information. Often it's open only on weekends, but check the page to be sure. [it seems to be open tues-sun in Sept]
Sint-Jansstraat (Wildert) 238
2910 Essen, Belgium
+32 3 677 22 67
From Google Maps, it seems that it is about 6km from Essen, Belgium train station, heading south. So, I don't know how you would get there via public transportation. It would be a very easy bike ride from the Essen station. The web page says it's 30km from Antwerp and 65km from Rotterdam.