  The classical concept of affine locally symmetric spaces allows a
generalization for various geometric structures on a smooth manifold. We remind
the notion of symmetry for parabolic geometries and we summarize the known
facts for $|1|$--graded parabolic geometries and for almost Grassmannian
structures, in particular. As an application of two general constructions with
parabolic geometries, we present an example of non--flat Grassmannian symmetric
space. Next we observe there is a distinguished torsion--free affine connection
preserving the Grassmannian structure so that, with respect to this connection,
the Grassmannian symmetric space is an affine symmetric space in the classical
sense.
