August 24 is National Waffle Day, a celebration of the day the patent on the waffle iron was issued. We use it to celebrate the waffle slab; we are not usually fond of concrete because of its carbon footprint, but waffle slabs let designers get much larger spans with less material. They also look so nice as architectural elements that they are left exposed instead of getting covered up with drywall- the structure is the finish.
Concrete slabs get thicker as spans get larger because the steel at the bottom is in tension while the top is in compression. Waffle slabs are designed to be thick where you need it, for the structure in the ribs, and thin for the slab.
Some of the waffles I have feasted on:
One of the yummiest waffle slabs I have seen is at the Montreal Museum of Fine Arts; you don't usually see them is spaces with ceilings this low. It adds so much drama to the space and puts paid to the argument that waffle slabs are hard to keep clean; it depends on where they are used.