The Xel'Naga Tower (Also known as the Xel'Naga Watch Tower, Watch Tower or Observatory) is an indestructible neutral structure that reveals an area of radius 22 around it when activated by a unit.
Xel'Naga Towers are usually placed in strategic locations of the map to provide advantages for the owner, such as:
- Covering base entrances (example: Shattered Temple)
- Covering high traffic path/areas (examples: Scrap Station, Xel'Naga Caverns)
- Covering important expansions (example: Backwater Gulch)
Due to the extremely large area of vision that the Xel'Naga towers provide, they are a very important point of control on most maps. Because of this, these towers are an often-contested location in many games; with each player trying to gain the most information about his opponent, while denying such information being revealed about themselves at the same time.
Scouting is such an essential part of StarCraft II, so the valuable information that the Xel'Naga Towers can reveal will often lead to better decision-making and faster reactions on the part of the player who controls them.
- The Xel'Naga Tower does not detect cloaked units.
- The Xel'Naga Tower will activate and remain activated while a unit remains within 2.5 range.
- When two enemy units are within activation range of a Xel'Naga Tower, it will deactivate.
- Burrowed and Flying Units cannot activate the Xel'Naga Tower. Cloaked units can.
- Summoned units such as Changelings, Infested Terrans can activate the Xel'Naga Tower.
- Buildings cannot activate the Xel'Naga Tower. This includes Auto-Turrets, and Spine Crawlers and Spore Crawlers, regardless if they are deployed or walking. Bunkers will also not activate the tower, even if units are inside.
- A worker idle within range of a Xel'Naga Tower will not be reported as an idle worker by the UI, and will not be selected by pressing Ctrl-F1.
- A Siege Tank still activates the Xel'Naga Tower while in Siege Mode.