Watchtowers are set at regular intervals along the raised roads of the Guarded Land. They form not only the primary communications systems of the Commonwealth, but also provide the Wise with a 'sensory grid' with which they 'see' much of what goes on in the Guarded Land. In addition, each tower is garrisoned with enough auxiliaries to defend the gate over which each tower stands guard.

The communication system has two distinct aspects. Messages can be carried as sealed despatches at furious speed along the leftway by couriers who can obtain fresh aquar at each tower. Couriers and what they carry are protected by stringent codiciles of the Law-that-must-be-obeyed.

Even more rapid are encoded messages jumped from tower to tower by means of the heliographs during the day or naphtha flares at night.

Many watchtowers are the centre of extensive stopping places where the crowds travelling on the road below can make camp for the night

Watchtowers play a large role in the Stone Dance and it was because of this that I felt the need to understand their exteriors and interiors so well.