“the site consists of at least 20 huge shafts, more than 10 meters (32 feet) in diameter and 5 meters (16 feet) deep, forming a circle more than 2 kilometers (1.2 miles) in diameter.”
32 feet across could have been roofed, and wooden structures inside like a floor or two (possibly a basement for animals) could have provided earth-sheltered (moderate temperature) food storage and lodging for pilgrims/festival attendees.
If there were animals, there’ll be poop. Lots of it. I grew up on a dairy farm. I know poop.