There wasn't much else to do at the time, so slot car racing was pretty popular.
Oops, I meant GO CART TRACK, not SLOT CAR TRACK. Still attracted the same crowd.
Oh hell, it was OBVIOUSLY a large, outdoor game room. See, ya knock over one of the T-shaped thingies...then it falls into the next one...then the next one....you know; like dominoes.
Then....then.....young men had to show their bravery and manhood by attempting to stop the falling stones with their penises.
On average, how successful were they? Glyphs have been deciphered that made reference to a very large number of sopranos in their choir.
Read the cover story article in National Geographic Magazine. Interesting part was there is no entrance way to the inner circle.