When your map is populated with makers you can define a radius based on a point and a radius.

Loaded markers : 0

This map have a fixed center and the markers are from Sobipro.

The radius is defined by a select list, and the center point can be selected by a right click on the map or by entering any value in search input.

Note that you can limit the prediction to one country. On this map we have limited this prediction to the USA. Try to enter Paris (you will not see Paris, France).