Tsívangaan

Tsívangaan is obviously an artificial world, with its cylindrical layout. Living inside a giant barrel isn't natural! And when I say giant, I mean over 100 Km across (over 60 miles), and much longer than that... and there may be several of them, linked together. Why are there saber-tooth cats, dinosaurs, and cavemen?

Can a professor from the 22nd Century and a hippie from the 1960s survive?