I am redoing my small galley kitchen. At one end of the main counter
space, there is an opening in the wall through which one end of my new
countertop may flow (the opening is at the same height as the
countertop; also, the opening is the same width as the countertop). The
opening serves as a window into the dining room area.

I was wondering whether to extend the new countertop through that
window into the next room? Or, should I stop the countertop flush with
the inside wall of the kitchen--and then create a window sill for the
opening/window?