Rhyl is a nucleated settlement Photograph: Don McPhee

Nucleated settlements are towns where buildings are close together, often clustered around a central point. The location of a nucleated settlement can be determined by a range of factors, including being easy to defend, close to a water supply or located at a route centre.

A nucleated pattern often develops where defence is a priority, such as inside a meander (a bend on a river) or on a hilltop (for instance, Caerphilly). Cardiff

Villages that are situated by a water supply often grow into towns, for instance Taffs Well, or Ffynnon Taf in south Wales. Nucleated settlements also develop higher up a slope to avoid flooding.

Often we see nucleated settlements where people have settled on flat lowland areas, where the town can expand in many directions.

Route centres often create settlements with a nucleated pattern which grow up around a crossroad. Due to urbanisation and site factors, many settlements will expand quickly.