The image above in the Sea of Tranquility (Mare Tranquillitatis) was taken by the Lunar Reconnaissance Orbiter while the Sun was almost straight overhead, illuminating the region. By comparing this image with previous images that have different lighting angles, scientists can estimate that the pit is about 100 meters wide (the size of a football stadium) and about 100 meters deep!
Locate at 8.33 N, 33.22 E, it’s about 375 kilometers northeast of where Neil and Buzz landed back in July of 1969. Imagine how different Human history and space exploration would have been if they’d seen this off to the side at pitch over!!
While common thought is that it’s a skylight into a lava tube, there are no obvious volcanic features near by. It may go on for thousands of meters, providing tens of meters of shielding from radiation for those living inside it!