To put things in perspective, here's Earth's currently largest land vehicle, the RWE Bagger 288 excavator.
It meassures up to 220m long and 96m high, which would put it approx. the size of Stargate Atlantis Daedalus Class starship, a Babylon 5 Drakh Hordes Raider, 80 meters short of a Rebel Alliance Nebulon-B Escort Frigate and 70 meters short of a Star Trek Constitution Class starship (the original Enterprise)
Here it is in robot form (although I can't find the specs for that):
This is the Oasis of the Seas, 360m long, which is 10m longer than a Drazi Sunhawk Class starship or The Shadows Scout Vessel from Babylon 5. It's also 60m longer than the Star Wars Nebulon-B Frigate. 70m longer than the original Enterprise, 280m shorter than the Next Generation Enterprise.