im sure youve seen this somewhere already but look at this if you ever make something about citadels
https://web.archive.org/web/20190612070301/https://forum.facepunch.com/games/udzt/A-short-guide-to-mapping-in-Combine-architectural-style-for-HL2/1/
https://web.archive.org/web/20190612070301/https://forum.facepunch.com/games/udzt/A-short-guide-to-mapping-in-Combine-architectural-style-for-HL2/1/