Galois involutions and exceptional buildings

Abstract

We apply the theory of descent for buildings to give elementary constructions of the exceptional buildings of type $A_2$, $B_2$, $C_3$ and $F_4$ as the fixed point building of a Galois involution of a building of type $E_6$, $E_7$ or $E_8$ or, in one case, a pseudo-split building of type $F_4$.