In the morning I took a walking tour of the city which was excellent. The tour guide was a bit dramatic but he did have a lot of incredible facts about the city. This is an old apartment building. He told us all about how in the medieval times the first level was a shop and then on the floor right above that would have been the richest and each floor would have become more poor as you went up. Completely opposite from today, but it was due to the lack of fire escapes. The closer you were to the street the better chance you had of survival in case of a fire.
Around the back they had exposed these ancient steps to demonstrate medieval burglar alarms. You can see that the middle step in this stair case is really short. This is a trick step. Those living there would be aware of this and step over it, but in the night if an intruder entered they would trip and alert the family of an intruder.