Not the main street in Itaewon, but closer to the Noksapyung Subway station.
OR out the Kimchi Pot Gate.
I have a couple of friends that just LOVE, LOVE, LOVE this place.
And their presentation is very nice!
Pizza slice at top: 4 cheese pizza - 4 different types of cheese, but in the four corners (scratching head on that one!) Middle: pretty good, mushroom pizza and bottom: margarita pizza - seems to be missing a few things.
From the Kimchi Pot Gate:
Exit and take a right.
Go down and cross the street.
Come out on the right exit and walk just a few feet and you will see Trevia on your left.