Norman architecture
The Normans introduced large numbers of castles and fortifications including Norman keeps , and at the same time monasteries , abbeys , churches and cathedrals , in a style characterised by the usual Romanesque rounded arches ( particularly over windows and doorways ) and especially massive proportions compared to other regional variations of the style . 
<triplet> castle <subj> fortification <obj> subclass of <triplet> keep <subj> fortification <obj> part of