Hierarchy classification:

1. top of the aat hierarchies
2. Objects Facet
3. Built Environment (hierarchy name)
4. Single Built Works (hierarchy name)
5. single built works (built environment)
6. [single built works by specific type]
7. [single built works by function]
8. fortifications (built environment)
9. forts

Anotations

Scope note:

Forts having a polygonal shape, which varied according to the site and requirements. Although they existed by the middle ages, prime examples of polygonal forts were those constructed resist the fire of rifled artillery and heavy mortars in the late 18th through 19th centuries.