I'm thinking construction of such a beast would have to be done in a special way given no dry dock (or harbour for that matter) could handle such a beast. How big do you estimate this beast would have been in the real world?
For comparison, the longest ship ever constructed was the Knock Nevis supertanker which 458m long with a displacement of 646,642 long tons full load.


In the above diagram, we have:
- The Pentagon, 431m (Light blue)
- RMS Queen Mary 2, 345m (Pink)
- US Navy's nuclear-powered USS Enterprise, 342m (Yellow)
- Airship LZ 129 Hindenburg, 245m (Green)
- Imperial Japanese Navy's Yamato, 263m (Dark blue)
- Empire State Building, 443m (Grey)
- Apple Park main building, 464m and 354m diameters (Green)
- Knock Nevis supertanker, 458m (Red)
This ship has an interesting history going through various names and owners in its 30yr life. Perhaps most interesting is the fact that it was damaged and sunk in 1988 by an Iraqi Air Force attack while anchored off Larak Island, Iran. The ship was struck by parachute bombs. Fires ignited aboard the ship and blazed out of control and it sank in the shallow waters off the coast. It was declared a total loss and was written off. Later on though it was salvaged and repaired and re-entered service in 1991.