Mark was really helpful and responded immediately when I had difficulty working out how to get into the flat. There is an exterior door with no means of getting in unless another resident of the block allows you access. Also it was not made clear that when you have found Mark's flat, you have to enter the door entry code twice to open the door. However, unlike some previous reviewers, I found the lift working and the whole building beautifully clean. Overall I would recommend the flat as a great base for a visit to central Paris.