Architecture in Europe during 373 to 500 AD changed from rectangular basilica forms to Byzantine.  This style was more like the Romans and was popular in 700 to 1200 AD.  The churches were designed around a theme of centralization, which was round, cruciform, or polygonal in shape.  Martyria were erected on sites that had a special meaning in Christ's life and other places that held sacred because of the sacrifice of martyrs.