Layout
Atlantis is a huge, snowflake-shaped platform covered in skyscrapers; at the center is the central spire, the tallest building in the city. The central spire contains the main control room, referred to as Stargate Operations (also called the Gate Room), and the Stargate itself. Rapid access throughout the city is provided by a network of transporter rooms. The underside of the city contains the massive engines that propels the city through space, as well as the docking point for an Ancient outpost.
According to Visual Effects Artist Bruce Woloshyn, the model of the city of Atlantis, when they first built it, was over four million polygons - feature film in size. There is thus a lot of detail that they can back up, allowing the city to look really nice, even from an extremely close view. Also, most of the city is modelled, not textured, which allows for the details to move when the city is turned around.
Many sets used for Atlantis (and also SG-1) are actually part of a massive sound stage which was built for almost 2 million dollars. This large stage is used for rooms like the brig, several balconies including the ones with the grounding stations or other interior parts of Atlantis. If they require outdoor views they use green screens to hide parts of the set. Also some sets of Atlantis are part of the set which was used for Blade: Trinity, for example the bridge seen first in "The Storm" or the infirmary in "Michael".
Read more about this topic: Atlantis (Stargate)