Rampant Rook

Ouch.

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.

16. Kc1 Rc2+ and black must capture the rook for stalemate.

After Rc2 Black plays Nxc2#, Grobe...

Ra1#

Yes, yes that's true.

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....

It was drawn until black reached the bishop

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.

It's a draw by perpetual.

It is, but not in the line shown.

The white king in stalemate cause black has so many pieces. The white king is poorly positioned and only his goal is to draw. To draw, white rook has to check forever. If black captures a white rook, it is the draw.