In the USA the term control zone is no longer used[1] and has been replaced by airspace class D. Typically it extends 5 miles in diameter with a height of 2500 ft AGL (above ground level) around small commercial airports.
In the UK, control zones are normally class D airspace and usually extend from the surface to 2000 ft AGL.
They can be observed to be usually rectangular, extending along the axis of the main runway, although irregular shapes may be used where more complex airspace dictates this (see Liverpool and East Midlands).
In Germany, control zones are a special type of class D airspace, called D (CTR).
The main difference to the regular German class D airspace is, that within a CTR there is a minimum required cloud ceiling of 1500 ft AGL.