The sparsely wooded land of loess hills is crossed here from southeast to northwest by the Emsbach, which is fed near Niederbrechen by the Wörsbach and drains the area down to the Lahn.

Very early in Brechen's history, there was a Roman military camp in what is now the municipal area, at a site now known as Alteburg (“High Castle”), lying on the Emsbach.

Lying near a group of Hallstatt-era barrows, the site had long been known to contain something historical, but since it had never been properly investigated, it had always been taken to be a sconce from the Thirty Years' War (1618–1648).

The latest investigations have yielded the knowledge that this site was girded by a typical Roman V-shaped ditch, within which spread an area of roughly two hectares.

Private finds from this area point to the likelihood of a marsh camp from Augustus’s time In a donation document from the Lorsch Abbey dated 12 August 772, Niederbrechen and Oberbrechen had their first documentary mention under the name Brachina (“at the mountain slope”).

Brechen has, however, developed into a residential community, 90% of whose working inhabitants earn their livelihood in surrounding towns, mainly in the Frankfurt Rhein-Main Region.

Niederbrechen and Oberbrechen stations lie on RMV line 20 (Main-Lahn Railway) between Limburg an der Lahn and Frankfurt am Main.