Going down from the Castle of Bosa along the slopes of the hill and through the cobbled streets and trachyte steps, you cross this old quarter.
The old town centre of Bosa has kept its appearance unchanged over the centuries and what stands out from the view of the town is the vision of many small coloured houses that form the Sa Costa area that from above the Malaspina Castle goes down to Via del Carmine.
The medieval village Sa Costa is the ancient part that dates back to the XIII century. It is made up of four main streets that follow the altimetric curves of the hill and several cobbled lanes, with trachyte steps that interrupt the horizontal route. It is bordered by two long stairways called S’Iscala Longa to the west near Piazza Carmine and S’Iscala e sa Rosa to the east which can be accessed from Piazza Episcopio and then Corso Vittorio Emanuele, the main street in the centre of the city.