Architecture applies to both the construction of such buildings, and the gauging of building's quality.
Ability Score(s): Math
Usage: Whether using this for building or for identifying a building's quality, the Architecture skill allows for finding weaknesses or creating blueprints for the construction of new buildings.
Building quality is determined by how old it is, and how well it has been maintained. Typically identifying a building's quality is a DC 20.
The quality DC is decreased by 10 if the building is abandoned or in shambles/destroyed, or decreased by 5 if it's poorly maintained or overtaken by nature (if the building isn't already natural like a greenhouse). Quality DC increases by 5 if the building is especially magnificent (most castles and well made churches) whereas the DC increases by 10 for especially impressive works of architecture (impressive fortresses, wizard towers, and massive cathedrals).
Architecture can also be used to build buildings, doing so is often a lengthy process and is a Skill Scene which takes months or even years to complete. You are the blueprint of this project, the mastermind, and often don't do the bulk of the work but instead learn and understand how to make buildings and make them last.