Pit-stop in Brussels

If you only have a brief period, the best thing to do is explore the old area around the Grand Place. From Midi you may be able to get a train to Gare Centrale depending on your ticket, if you have separate tickets for the two legs of your journey. If not, get the metro from Midi to Bourse station, although that will need a separate ticket. Meal recommendations depend on your budget. If you have a fair amount of money go to Aux Armes de Bruxelles or Vincent. If you can't afford those two don't eat in any of the other restaurants around rue des Bouchers, which are notorious tourist traps. The Roy d'Espagne restaurant on Grand'Place itself is a bit cheaper and has a good view of the Place if you have a window seat.

As far as chocolates go, beware of the tourist trap shops in the streets around Grand'Place that sell no-name chocolate at inflated prices. Just off Grand'Place is a branch of Galler, which is one of the better chain stores. The Galeries St Hubert to the north have a branch of Neuhaus, which is my personal favourite chain. For the really good stuff, either head northwest to the St Catherine's district and go to Blondeel's on the Place St Catherine, or head southwest (a much longer walk) to Grand Sablon for Marcolini or Wittamers. I read very good things about Laurent Gerbaud who has a shop near the Bozar arts centre, but have never tried myself.

Neuhaus is my favorite chocolate, there's a small shop in the Grand Place. You can also order online, delivery is via Fedex.

Try the fruit beers (my favorite is cherry).

I agree with Philip that the Gare Central would be a better station to start from, if you could just get off your train there and work your way down to the Gare du Midi, about 2 km/1.2 mi from the Central Station. A five-hour trek from the station should include the Grand Place, certainly one of the remarkable public squares of Europe. The Place de Petit Sablon is another rewarding outdoor place to visit on foot.

You probably won't want to spend much of your brief stay in museums, but the Royal Museum of Fine Art, Musical Instruments Museum (MIM), and Belgian Center for Comic Strip Art are all rewarding, depending on your tastes.The comic art museum is in the opposite direction from your route to the Midi Station, though.

Food: Like Philip, we enjoyed supper at Aux Armes de Bruxelles. A half-bucket of mussels and a Grembergen Brune at L'Estaminet du Kelderke at the east end of the Grand Place would be nice as a mid-day meal. Try to find a Chimay Bleu beer while you're in Brussels, too. The terrace restaurant on top of the MIM is nice, with great views, and you can get there without paying to go through the museum. For an artery-clogging and endemically Belgian snack, try the great frites at the Friterie Tabora. Just use that name on Google Earth to find the location a couple of blocks northwest off the Grand Place. If you want a nice mid-day break from rich tourist food, try the Exki in the triangular plaza just a block up from the northeast corner of the Grand Place.

Your path probably should pass by the Mannekin-Pis, although you later will ask yourself why you took the time to see a statue of a boy peeing. It's the icon of Brussels for some reason, and the rest of us just go along with it. To strike a blow for gender equality, there's a similar girl statue in the city. There's a bronze peeing dog statue. Stay tuned for news of other species. Brussels statuary cries out for doctoral psychiatry dissertations.

Any statue that has over 900 costumes is worth at least a quick look!

Thanks everyone...this is really helpful!!