Don't let the outside fool you, because this warehouse has been renovated into a shopping mall!
Having been here a few times, it is always crowded, but the shops are unique and sell very nice and interesting things like glassware or jewelry and accessories. I think if you're planning a trip to Yokohama this would be a nice stop during your day. A lot of times there are events planned outside (festivals, live performances etc.), so if you're lucky there might be one when you visit!