Rampant Rook

So after 16...Kc1, how is it a draw?
Good Question! The Rook should never allow the King to cross the 4th rank

Indeed, the current position looks like a win for black after either 16. Rxd1+ Qxd1# or 16. Rg2+ Kc1 when mate is inevitable.

This is the part where I say I knew that all along, and that it's precisely what I meant when I said "Ouch" in reference to accepting a draw in a won position -- being careful, of course, to edit my other posts appropriately....

They key to this draw is to keep the rook on the 4th rank delivering check at every turn unless the king goes onto the b-file after which you need to keep the rook on the c-file, continuing to deliver check.