In general "The Watchtowers" are the home of the 4 main Elements - Water, Fire, Earth and Wind. They're the 4 cardinal points of a compass - East, South, West and North.
The Watchtower of the East is the home of the element Air and the Watchtower of the West is the home of the element Water.
This is regardless in what hemisphere we live in.
The Watchtower of the South is the home of the element Fire and the Watchtower of the North is the home of the element Earth. But this is only for the people living in the Northern hemisphere; for the people in the Southern hemisphere it's the other way round.
The Watchtowers also house other beings associated with the directions and elements - Sylphs, Undines, Salamanders, Gnomes, angels, etherial beings, faeries or deities. …show more content…
This is where we call the Elements from while we're doing rituals.

As I see the word "Watchtower" anyway as a word which describes something, that is protecting, I see "The Watchtowers" as guardians. In normal life watchtowers are built at coasts to protect boats and ships, so they're protectors.
They and the elements in them can protect me while I do rituals. And as the house the four elements and within them the four directions I also see them as a kind of totality - they connect the whole universe.

In the Pagan and Wiccan community the Watchtowers are seen as look outs or protectors of that special area (direction), that is where we call the Elements from when we're casting our circles and performing rituals. So they're seen as guardians of the magical circle.
They're associated with the four cardinal directions.
In the Christian community and also in Christian influenced traditions the Watchtowers are the home of the Archangels (Uriel, Raphael, Michael and Gabriel).
Also in the archaic Roman tradition a kind of watchtowers could have been found: small towers were built at the crossroads and altars were set before