His lanza completely dwarfs Las Noches, which was big enough to take 3 days to walk from presumably one corner to another:
Calcs can get a bit wacky but going by Nel’ls statement it’s pretty obvious that Las Noches is far bigger than a City and more closer to being the size of a small country, which looks like the most accurate estimate.
That puts R2 Ulquiorra laughably above mountain level.