Pisa cathedral_The stairs in the drum: the constructive connections between the dome and the loggia

The loggia at the base of the dome can be reached by two staircases created in the east and west sides of the drum: they start from the garret of the central nave and, via a single ramp, lead to beneath the vaults of the loggia. The two staircases have a similar position; they are accessed from the corners of the octagon of the drum, one between the west- and north-west sides and the other between the east- and south-east sides. The paper explores the relationship between the stairs, each in its specific constructive context, and the dome