Nibbāna:
(5) "Just as, although the rivers of the world flow into the great ocean and showers of rain fall from the sky, no lessening or filling up of the great ocean is evident, so also, although many bhikkhus attain final Nibbana in the Nibbana-element with no residue left, no lessening or filling up of the Nibbana-element is evident. This is the fifth wonderful and marvellous quality in this Dhamma and Discipline… Ud5.5
Sounds like it is something more than just nothingness, I would say.
With metta