There is a clear distinction between what may be called Phenomena and Noumena is that the former is an empirical object conceptually determined while the latter is strictly an ontological object constructed by the intellect. The reasoned extreme of the noumena is the transcendental object that is not only purely an intellectual ontology but an unknown one. The Transcendental objects very being is driven by the limiting function the noumena has on phenomena, the habit of calling things in themselves noumena - it is by this habit the intellect limits itself and in doing so too limits its understanding.
I can think of no object better fitting of this description than the singularity whose conceptual limitation is the Schwarzschild radius. The Schwarzschild radius is the boundary between phenomena and noumena as it is the material manifestation of empirical limits. At that radius definition and categorization is concrete while beyond that boundary we enter speculation and as consequence all understanding is derived strictly from the intellect, hence beyond that boundary we enter the realm of noumena. The singularity, something which makes very little physical sense in the understanding, is merely a name for an unknown something and as such it is Transcendental in the strictest sense.
