Jim W.
Yelp
This is highly worthwhile, especially if you are interested in history / the battle itself.
I try to do appreciable advance research relating to our trips. However, there are sometimes levels of detail that are not evident until you experience things first hand. So as an introduction to this site, I'll first discuss travel logistics.
Assuming that you are staying in Brussels without a car, you'll need to take a train / bus combo to visit this site. Trains from Brussels Central or Noord run fairly frequently to Braine-l'Alleud. You can probably get one within 30 minutes or so of walking up, but you may want to consult a schedule. The out there takes around 30 -35 minutes, I think. You purchase this ticket from a machine via a credit card (I'm not sure if there is a way to purchase with cash other than finding a human-staffed desk at a large station). I think the fare was in the neighborhood of 10 Euros.
Once you reach Braine-l'Alleud, you walk directly from the platform across a small parking lot to a street. Across the street is the stop for the 'W' bus, which will take you to the battlefield. The stop is between a Chinese restaurant and a motorcycle dealer (when we went). The bus runs roughly every 30 minutes and there is a schedule posted at the stop. It varies between weekdays and weekends. There is also an app you can get (my daughter found it) that lets you track the buses in real time. We saw a bus pull away just as we exited the station, so coordinating the schedules would have saved us a few minutes.
The crucial detail that we missed was that bus far is cash only - no credit cards. It was our last full day and we had tried to spend our Euros so as not to have too many left. Hence, we could not ride this bus! We got off and found an ATM across the train tracks. We obtained 25 Euros to have some buffer. The bus fare one-way to the battlefield is less than 3 Euros per person. We got back and waited for the next bus, which we then rode to the battlefield. The total route on the bus is probably about 1.5 miles and there are sidewalks the whole way. Later, we noted tha the return bus was delayed by 30 minutes, so we ended up walking back to the train station from the battlefield. It wasn't a bad walk.
As to the battlefield and museum itself, here are the highlights:
* I bought tickets in advance, but it didn't seem like that was necessary on the day we went. These were not timed, but were good for the entire day. It doesn't hurt to have them, though. The museum is built underground, perhaps so as not to disturb the views of what the battlefield looks like. There were references to audio tours and some app that you could have downloaded to help with the visit but we didn't see these until we were well into the exhibits. You may want to ask when you arrive. The layout of the museum first a short high-level timeline of how the battle came about - monarchies, the French Revolution, and the rise of Napoleon. This is covered in 2 - 3 intiial rooms. You then move into a long hallway that slopes slighly up as you go. Along each side behind glass are manikins dressed as representatives of the states engaged in the battle. Some are mounted on horses. The timeline here is more dense, showing the maneuverings in the days leading up to the battle itself. You can then view a 10 - 15 minute 3-D film about the battle, which gives you even more of a feel for it. If you have the audio tour, you may get translations for the French / German bits also. After the film, you can check out some details about the aftermath of the battle, as well as an animated bird's eye view of the engagement.
* The Panorama - This is a huge painting that wraps around to 360-degrees and attempts to tell the story of the battle. This is housed in a large round stone building adjacent to the museum. Apparently, this type of painting was popular in the late 1800s (pre-movies) and traveled to various cities. There is also one related to the U.S. Civil Ware in Atlanta, GA. I think there is one at the Gettysburg battlefield in Pennsylvania as well. Having seen the one in Atlanta a few times, this was neat to compare.
* The Lion Mound - a memorial to one of the fallen nobles/military leaders. This is about 130 feet high with over 200 steps leading up. It was a workout, but has nice views at the top.
* Hougoumount Farm - this place figured prominently in the battle, and is preserved as a separate site. It is about a mile from the museum and can be reached by a wide paved path. They have a regular shuttle cart (think of the type that cover huge parking lots in places like Disney World in the U.S.) that runs at ~ 25 minute intervals. We walked out to the site and took the tram back. The site has some exhibits and is worth the short side trip if you have time.
They also have a café and table-service restaurant on-site. Go early (before 12:30 p.m.) for the best chance of service. There are few other walkable eateries