Hyperpolar homogeneous foliations on symmetric spaces of noncompact type
  A foliation on a Riemannian manifold is hyperpolar if it admits a flat section, that is, a connected closed flat submanifold that intersects each leaf of the foliation orthogonally. In this article we classify the hyperpolar homogeneous foliations on every Riemannian symmetric space of noncompact type. 
J. Berndt, J. C. Diaz-Ramos, H. Tamaru