We recently stayed in Castelo for 3 lovely days. There was an mix-up with our booking, that we learnt about upon arrival, but the Castelo team did everything to accommodate us in the best way possible, so there are absolutely no hard feelings, on the contrary - we are very grateful for their hospitality!
The hotel itself is very unique. A true gem in a rather good location. It is located a few minutes away from Marques metro station (yellow line). Easy access to/from the airport (taxis were on strike during our visit); takes approx 40 min with a change at Trindad, but reserve an extra 20-25 min, as the trains to the airport are not that frequent. We also used uber while moving around the city; works perfectly fine and is rather cheap. Rua Santa Catarina is a very busy street, but the hotel is located up the hill, that part is very quite.
The rooms are spotlessly clean and the ones in the modern building are very spacious. Good quality of towels and sheets, nice toiletries. The staff is lovely, very smiley, friendly and helpful.
We did enjoy the daily breakfast, especially a nice selection of fresh fruit. The breakfast room is very special! So is the whole territory, very beautiful and immaculate. If Castelo had an outdoor swimming pool, I would give it 6 stars!
We were genuinely happy with our stay. Thank you!

The agent at the reception desk (who did both our check-in and check-out) was extremely rude, he didn't tell us anything about the property, nor did he welcome us at 2 pm when we got there or bid us farewell upon our departure... I informed him upon arrival that the bath in the Royal Suite (room 122) was not clean - there were black hairs in it -, he shrugged his shoulders and stated that the maid had cleaned it; and that was it! When we got back that evening, the bath was in the exact same state in which we left it... There was also dirt on the carpet under the bed, as well as encrusted black hairs all over the hairdryer... not very pleasant... The shower was very narrow and had no shower curtain, making it difficult to move freely... Besides, the hairdryer had to be activated manually, by continually pressing a button, which is inconvenient if one has long hair, taking a while to dry... I got finger cramps after each shower!... The ventilation in the bathroom was by the way insufficient, humidity was accumulating very fast. In the room, the furniture was decorative only, and very hard to use because of its age and impressive dimensions - opening the closet door, for instance, was a hassle, as some piece always threatened to come off... As for the bed, it was hard as rock and very uncomfortable. The big pillows were also too firm, impossible to sleep on! The sound-proofing was non-existent - we could hear the toilet being flushed upstairs, people talking in the corridor (once, a happy party woke us up at midnight!), and even the traffic outside... It proved a real challenge to get a good night's rest. The fridge turned out as superfluous as the furniture, for it did not cool anything... I needed it to store some medication, and it proved utterly inefficient... Moreover, there is no air conditioning in the common areas of the hotel nor in the breakfast room, which can be very uncomfortable on hot days, as well as inappropriate for the food, stored at such high temperatures for the duration of the breakfast. Lastly, the hotel is situated far from the river bank (35-40 min by foot) and fairly far from the city center (25 min by foot), which is distressing on heatwave days. Unfortunately, there are very few positive aspects to this hotel (breakfast, air conditioning in the room), which has otherwise proved a HUGE DISAPPOINTMENT on all fronts : if the atmosphere is authentic and the gardens carefully tended, the facilities inside the Castle are archaic & unpractical and the staff, utterly IMPOLITE! The only suggestion I can make is : "Go elsewhere!"