Atop Mesa Verde, in addition to cliff dwellings, like Cliff Palace, that were built hundreds of years ago, there are other, older settlements, like the ones at Far View. Archeologists are still learning about these older structures and the people who built them, and in their most recent discovery, researchers found that a structure that was once thought to be an ancient reservoir actually couldn't have held much water.
The area was thought to be a reservoir by one of the first people who analyzed it in 1917. (They also named this "Mummy Lake"—now it's officially called the Far View Reservoir.) But scientists examining the site today found this theory unlikely.
From Joseph Castro at Live Science:
They found that the ditches leading from Mummy Lake to the southern structures couldn't have functioned as water canals or irrigation distribution systems. The ditches would have easily spilled water over the canyon edge at various points if it didn't have walls controlling the water flow (which don't appear to have existed).
Next, the team used climate models to investigate Mummy Lake's potential to store water. They found that even in the wettest year on record, 1941, the pit would have gotten less than a foot of water from winter and spring precipitation by the end of April. This water would have completely evaporated by the end of July, when it's most needed for crops.
That’s bad news for the American Society of Civil Engineers, which designated the Prehistoric Mesa Verde Reservoirs as a Historic Civil Engineering Landmark in 2004.
So if it’s not a reservoir, what is it? The researchers believe that the "drainage ditches" are actually roads into the structure, indicating it had some importance to the community. The shape and size suggest a ceremonial gathering place, similar to other kivas in the Southwest.