Sky City

Basic
Sky Cities are the best defense in Hardmode against the Corruption and the Hallow for your homes and NPC's. They are completely detached from the surface and when lit properly, protect against almost all enemy spawns. With Small maps it is PROBABLY best to use synthetic blocks to prevent Corruptors from infecting your City, however Medium and Large maps are likely high enough to be safe. [Need Proof and Picture of basic example] Levels are determined to prevent harpy spawns. For taller cities (100+ blocks) lower levels would be required.