Located between Ottignies-Louvain-la-Neuve and Gembloux, 40 km from Brussels, Chastre is well served by road and railway networks.

With its tributaries, the Orne creates enchanting landscapes, surrounding magnificent farmhouses, often still fully in use.

The former rises in Bertinchamps (Gembloux, province of Namur), and waters the villages of Cortil, Noirmont, Chastre and Blanmont before flowing by Mont-Saint-Guibert and eventually emptying into the Dyle, via the Thyle, in Court-Saint-Étienne.

The latter rises in Sombreffe, near Gentinnes, which it runs through, then crosses Villeroux and eventually empties into the Orne at Mont-Saint-Guibert.

It cannot be said that these two small rivers have made much of a dent in this part of the Brabant high plateau, which has an elevation of between 145 and 155 metres.

Due to its location between Brussels and Namur and to the high road and railroad connections, Chastre's countryside has had to face a strong urbanisation for more than 30 years.