I really enjoyed the Agharta section. Also water clocks have been around in China since around 4000 BC.
Music wise I enjoyed the soundtrack's use of leitmotif to bring things together as a whole, although I would have loved a few more themes scattered throughout. Also I was a little disappointed that the music at the start of the Necromancer's Abyss was only used once. Hopefully it will return in the DLC.
Sincerely,
David