Note that building D is huge (11 floors) and situated along "avenue DEPAGE",
where it is the only such high building.
The "Service de Métrologie Nucléaire" occupies the right
wing of first floor
(which
corresponds to level 3 in the lift).
My office (DB3.156)
is the last one of the corridor.
If you arrive by plane: the Central Station ("Gare centrale") is easily accessed from the Brussels Zaventem airport (nearly all companies but Ryanair): trein about each 20 minutes; if you arrive at "Brussels South - Charleroi", you will find bus connections to the South Station ("Gare du Midi").