Parabolic nilradicals of Heisenberg type, II

Every real simple non-compact Lie algebra not isomorphic to $\mathfrak{s}\mathfrak{o}(1,n)$ contains a unique standard parabolic subalgebra whose nilradical is a generalized Heisenberg algebra. Here we discuss the associated parabolic geometries and the riemannian geometry of the harmonic spaces having the former as conformal infinities.