It is a self-contained strong house, a defensible seigniorial residence usually with more than one suite of accommodation, a residence that would also be the whole castle. It had all the components, halls, chambers, chapels, and sometime kitchens all together into one compact unit, the result being an impressive tower. There were rectangular towers divided from top to bottom by a cross wall that gave structural strength to the whole and facilitated roofing. The principle suite do the lord himself was marked by extra ornamentation and sometimes rose through two stories to give extra space and light. The majority of those built in the 12th. Century were rectangular, but later the cylindrical donjon became fashionable, especially in France. This change from rectangular to cylindrical was a symbol of progress, the round tower being stronger in order to withstand the battering of missiles or the assault of pick and bore, and avoiding blind angles for the defenders.