In most basilicas, the central nave is taller than the aisles, forming a row of windows called a clerestory. Some basilicas in the Caucasus, particularly those of Armenia and Georgia, have a central nave only slightly higher than the two aisles and a single pitched roof covering all three. The result is a much darker interior. This plan is known as the "oriental basilica", or "pseudobasilica" in central Europe. A peculiar type of basilica, known as three-church basilica, was developed in early medieval Georgia, characterised by the central nave which is completely separated from the aisles with solid walls.