If Event Horizons can come in any number of dimensions (with the conventional things we call Black Holes having 2D of space-like degrees of freedom on the EH) that leads to the obvious conjecture that our 3D universe might itself be a 'manifold' (projection) from a higher dimensional 4D space (i.e. we live on a 3D EH). That 4D space might even itself be a projection from a 5D one, and so on. This is extremely similar to Holographic Principle, but very definitely a more generalized theory.