This is a terrible website. It gives you three different links/buttons to download the thing and wants you to sign in (e.g. with Google or Facebook) before granting access.
On a similar note, the Gigastructural Engineering & More mod for the space strategy game Stellaris adds a broad variety of fully visually modeled megastructures that sufficiently advanced space empires can build, ranging from academic theoreticals like Alderson disks to 'more gun' space combat uses like Death Stars to just-there-to-be-silly items like Discworld-style flat 'planets'.
If you like Tsutomu Nihei's megastructures and video games (specifically Half-Life 2 modding scene and old-school, retro-to-the-bone shooters), you should check out G String [1]. My 2020 GOTY hands down.
But an absolute go-to for lovers of virtual architecture is NaissanceE [2], which is free on Steam.
