I've been making the NYTs No-Knead Bread regularly, and this is the first time it happened - a sink hole. Really, it's not a bagel. It's a full loaf that didn't rise in the middle.
I think I know what happened. Spring has arrived with 80-plus degree temperatures. Instead of an overnight rest at 67 degrees, this loaf spent about 20 hours in the high 70s/low 80s. I suspect the yeast overpopulated their environment - exhausting starch resources then dying from starvation. I reinvigorated the outside by turning it with flour before letting it rise a second time. But not kneading meant not getting the new starch infusion spread throughout.
Still, it baked OK:
And it's very good. Chewy, crusty, tasty ... everything you could want in a bread, except whole grains. What can I say, a good loaf is my weakness.