Haven't been able to determine if any of the "hop on/hop off" Brussels bus tours include at least a drive-by of NATO headquarters. Does anyone remember seeing it? Thanks!

I don't think the hop-on/off buses go to NATO, but the airport bus line (nos. 11 and 12) drives right past it, and even stops there I believe.

Bus line 21 also goes out to NATO.

Yes, those regular bus lines will take you out past NATO. The 21 bus, as Hanl noted, is one of the buses serving NATO support staff. You might find the easiest place to catch the 21 bus over by the Rond Point Schumann, which is also in the EU area, so you'll see some of those buildings as well.

I didn't use the hop on/off bus, but you can wander on your own to the EU area and take a tour of the UN building. I did, and thought it was a bit blah ... but then the UN as a whole is blah and ineffective IMHO.

Extremely helpful - thank you -- I'll think of you with gratitude as I get on that bus!