Complex sentence: However, it seems the most important reason was mundanely technical: with a métro station, an RER station, and a motorway all situated directly underneath the "Arche", the angle was the only way to accommodate the structure's giant foundations.
Split into simpler sentences: However, it seems the most important reason was mundanely technical. With a métro station, an RER station, and a motorway all situated directly underneath the "Arche", the angle was the only way to accommodate the structure's giant foundations.