Mixing equipment known as a wet mill, its structure is similar with the dry mill, but Nianpan is no sieve, grind mound less, there is discharge organizations.

作为混合的设备称为湿碾机，它的构造与干碾机相似，只是碾盘上无筛孔，碾砣较轻，有卸料机构等。

youdao

And the first scene does suggest that we're starting at the very beginning: In a primordial swamp of sorts, brightly costumed frogmen bounce around and swing on a mound-shaped structure.

WSJ: Culture City: An Opera Vet Tries to Raise The Circus