My sister and I had a great stay at the Blue House @ Principe Real. The location is fantastic, just behind the Main Street of principe real, close to the garden, restaurants, shops and cafes. The barrio alto area where you will find more restaurants, bars and nightlife is a very short walk away. You can walk to two different metro stations or explore Lisbon by foot easily from here. Nuno met me upon arrival and was a great host, easy to contact and very welcoming. As other reviewers have commented, the apartment is located behind the main street , and you do walk through a small alleyway to get there. I stayed the first couple of nights alone before my sister joined me and I felt completely safe walking on my own to the apartment late at night.
The place was clean and tidy and the bed comfortable. The only comment I have is it seemed to be a bit damp so we kept the windows open to manage this, they have security bars so it was fine to do so.
Overall a great stay in Lisbon and we would be happy to go back again!