From Warhammer 40k - Lexicanum
Fortress Stations, also known as Ta'shiro in the Tau Language, are floating fortresses in the depths of space operated by the Tau Air Caste. These stations are positioned in the deep space between Septs, and have enough thrust to maintain a permanent position and resist drift. Several patterns of Fortress Stations exist, with the largest being comparable in population to a continent-sized city.
- 1: Codex: Tau Empire (6th Edition) pg.34