The permanent piece called "Meeting" at MoMA PS1 is an etherial experience of light and color and quiet. Sit and look through the cutout in the ceiling and watch the light change both outside and in. You can't tell what you're looking at until maybe a bird flies by.
Mekelburg's is equal parts hipster bodega, bar and sandwich haven. I always go for the cheese counter, the babka and the late night fried chicken sandwich, which is hands down one of the best I've had in NY.