Complex sentence: The fine arches with clustered pillars on which the tower rests are the glory of the church indoors, recalling the days when there were four guilds here, each guild keeping a light burning on these piers.
Split into simpler sentences: The fine arches with clustered pillars, on which the tower rests, are the glory of the church interior. They recall the days when there were four guilds here, each guild keeping a light burning on these piers.