The Termites Cathedral 'Watch Tower', performs the same function as a Chamber, it allows passage between the surface and the underground tunnels (see Chamber for more info).
However, the Watch Tower provides additional tactical defense by revealing an extremely large portion of the map(removing the fog of war) around it, it also has more health than a chamber.

Tip: this nest also shares a powerful special ability with the 'Elite Tunnel Guard' caste, read about the Elite for more info.

Cost: 140 food
Time: builds relatively quickly
Death: leaves an opening when destroyed