According to Genesis 6:14-16, Noah's Ark was 300 cubits long or about 510 feet long!
Scripture on The Ark's Length
Genesis 6:14-16 Make yourself an ark of gopherwood; make [a]rooms in the ark, and cover it inside and outside with pitch.
15 And this is how you shall make it: The length of the ark shall be three hundred [b]cubits, its width fifty cubits, and its height thirty cubits.
16 You shall make a window for the ark, and you shall finish it to a cubit from above; and set the door of the ark in its side. You shall make it with lower, second, and third decks.