Each section of wall is 60' tall and varies from 30' thickness at base to 18' at the top.
Conversion to approiximate metric - 20 meters x (10 - 6m), or average 20 meters x 8 Meters.
Each meter of face will have 160 cubic meters of material - which if granite will yield 2691kg x 160, or 430 metric tons per running meter. This mass is spread over an area of 20 square meters, so 8 cubic meters of stone per square meter of ground. Maximum compression is 21 metric tons per square meter, or 2kg per square centemeter. Since Granite can support between 1000 - 2000 kg per square centimeter maximum compressive force, it is able to handle a much higher wall then we have listed here. Of course, this is static forces and if there is any signficant moment of intertia, this can increase the stress greatly and possibly lead to structural failure.
When one considers the seven wonders of the world, one must obviously place the city of stoneholt at the #1 position - both alone from the size of its walls, and the quality of the buildings within. The contents of this city alone would constitute in excess of 7 wonders of the world!
The three kingdoms should have specific, not descriptive names. They can be described as North/ Center and South Stoneholt, but the people do not refer to themselves thusly. Go to Comment
A world whose lands are made up of huge terrain spheres that rotate constantly with most portion underwater. As time passes, the shape of the bodies of water change, landmarks shift inside the new border lines, and mountains tilt to different degrees. Land dwellers are gypsies that can never build anything permanent, and somewhat ironically, the only stable settlements are large structures built at sea.