40,000 cm = 400 m = 0.4 km ≈ 1 Empire State Building

Just in case you weren’t already clear: 20,000 Leagues Under the Sea refers to the distanced traveled while under water. Not to how deep the Nautilus dove. Earth isn’t even 2,500 leagues in diameter, so it wouldn’t work that way.

Fantastic work! I’d like to see more types of creatures in this style.