Complex sentence: The cathedral's exteriors are in relatively modern brickwork and are exceptionally plain compared to its elaborately decorated interior with wall paintings and gilded carvings beyond a wainscot of rich tile work.
Split into simpler sentences: The cathedral's exteriors are in relatively modern brickwork and are exceptionally plain compared to its elaborately decorated interior. The interior is covered with fine paintings and gilded carvings and includes a wainscot of rich tile work.