Thomas Grassmann and his son Sebastian have come up with one of the most plausible (and plausibly scaled) giant spaceships I’ve seen. Their Explorien Colony Ship can carry an entire pre-fabricated colony to a distant world. With a detailed interior and all the mod-cons this beast is certainly no lightweight. The best way to see it would definitely be in person but a perusal of the various folders should give some idea of the size and detail.
And if you’ve ever wondered how to take a photo of something this big, wonder no more. You use a tarpaulin.