Gigastructures ("gigas" for short) are insanely massive structures that can't be built by one person or even a large guild.
Gigas will require immense time, resources, and CLNY to build, and will depend on the help of the entire colony (or even multiple inter-chain colonies). Gigas unlock massive new feature updates, and everyone who participates in building them will gain free access in the form of a limited NFT.
Everyone who comes after a giga is built and wants to use it will also get to do so, for a small use fee (to help maintain the colony treasury, to burn, or sometimes, to reward the builders).