Other forms: commandingly
Something that's commanding is lofty, high, or impressive. Your thirtieth-floor apartment gives you a commanding view of the city.
In the old days, noblemen built their castles up high on hills so they'd have commanding positions over the surrounding countryside: in other words, the height of the castle gave its inhabitants a certain sense of dominance, both symbolically and practically. In the 16th century, this adjective meant "nobly dignified," as a commander might be, and by about 1630, it came to mean "dominant by virtue of size or position."