The building is indeed centrally location in the walled city. The service is excellent: Clara, the administrator, was there late at night to receive us and hand the keys, and Indira, the maid, pleased our requests and even went to the market to get groceries for breakfasts. Considering that it takes 57 steep steps to get to the apartment in the third floor, Clara had someone to help us bring the suitcases up and down.
However, its priviledged location becomes its only weakness: the noise. We were there for New Year's Eve, which is by definition noisy. It is surrounded by rooftop lounges. The windows in the apartment provide no noise reduction. The only way we could sleep was with ear plugs.
Additionally, while the apartment description states it sleeps 8, in the larger room there was a queen bed and an additonial twin bunk bed. We managed to accomodate the younger members of the family in the available beds, nonetheless.
I strongly recommend this place to young groups who want to visit Cartagena to party.