We characterise sets of points of exceptional Lie incidence geometries, that is, the natural geometries arising from spherical buildings of exceptional types \(\mathsf {F_4}\) , \(\mathsf {E_6}\) , \(\mathsf {E_7}\) , \(\mathsf {E_8}\) and \(\mathsf {G_2}\) , that form a line using the opposition relation. With that, we obtain a classification of so-called “geometric lines” in many of these geometries. Furthermore, our results lead to a characterisation of geometric lines in finite exceptional Lie incidence geometries as minimal blocking sets, that is, point sets of the size of a line admitting no object opposite to all of their members, in most cases, and we classify all exceptions. As a further consequence, we obtain a characterisation of automorphisms of exceptional spherical buildings as certain opposition preserving maps.
