Sub-Riemannian geometry is
the geometry of non-integrable k-plane distributions 𝒟 on n-manifolds M,
1 < k < n, where 𝒟 is equipped with a positive definite metric g. We classify the
simply-connected contact sub-Riemannian symmetric spaces (these belong
to a class of sub-Riemannian manifolds (M,𝒟,g) with special symmetry
properties).