Many of you have probably heard about the secret worlds in the original Metroid that are really just glitches, but accessible through different means (getting stuck in doors, emulators, game genie, etc). The are pretty well documented in the Metroid Database:

http://www.classicgaming.com/mdb/m1/secretworlds.htm

Castlevania, it was discovered a while back, seems to have similar secret levels that are accessed usually by using level edito programs and such. Often, it involves climbing up or a set of stairs that goes beyond the boundary of the screen (where there wasn't a set of stairs before or by extending an existing set of stairs..

My understanding is that these screens are hidden throughout the other NES Castlevanias too.

Does anyone know of a site that documents these (much like the Metroid Database does for the Metroid games)?

-Rob