The apartment is nicely furnished, spacious and has everything you need. Unlike the description (as of 09/21), it isn't located on the third floor but on the first floor. There is only a small staircase behind a metal door leading to the front door and terrace.
The apartment is located close to the main train station "Sao Bento". All the sights in Porto are within easy walking distance, which we enjoyed very much.
BUT: The apartment is located in a small, somewhat dodgy alley. Over the few days we were guests, we saw all sorts of things there. Human feces, vomit, condoms, a john along with a prostitute, in the evening hours also a junkie who has set his syringe. Especially at night, I strongly recommend taking the "upper" entrance to the alley. For solo travelers/women I would recommend the apartment for this reason only limited. However, the house entrance to the apartment (incl terrace) is behind a metal door, so you are safe there.