An example of an influence of Judaism and Christianity is Gothic architecture. Gothic architecture was first used in Christian churches in Europe during medieval times as a substitute for Romanesque architecture. Gothic churches included large, decorative windows that allowed light come in during sermons, while Romanesque churches had small windows and were dimly lit.
Another influence of Judaism and Christianity are the Crusades. Christians (whose religion originated from Judaism) fought against Muslims in the Middle East during the medieval ages to take back what they saw as holy land, and these wars resulted in hostilities that still exist today.