As mentioned, bentonite clay, hogs, or a sheepsfoot roller.
It seems your hole has been dug for a while, long enough for grass to grow, but I can't really see evidence that it's retained water yet.
I see a very well-defined horizon break where the soil layers change.
When you get a chance, post a closer picture of the soil profile and tag me. Can't really determine clay content from an image, but I might be able to notice something that may help.
