It is scarcely fair to base a review on one night in January, but this hotel has only a few reviews so it's better than nothing.
A good thing is that the hotel is very easy to find, though the map on the website is pretty useless. The hotel is in fact about a Km North of Mataro itself on the main coast road, the N11, so you really can't miss it. The building itself is set back about 40 m from the road but between the road and the sea is, of course the railway - the main East coast line - and trains are not infrequent. The receptionist was charming and recommended a mountain view room on the basis that it would be quieter and I couldn't see the sea anyway because it was already dark - good thinking! I went and looked at, and listened in a sea view room anyway, but then did the same in a mountain view room and agreed she was right. The sea view room had some degree of double glazing, but there were big patio doors opening onto a large balcony and the noise was certainly noticeable. The mountain view room was perfectly quiet.
The building itself is a somewhat indifferent example of maybe 1960s architecture - interestingly quite similar in many ways to the Panorama in Chania, Crete, which I have reviewed elsewhere, but much smaller. The owners have however filled the place with fairly convincing antique type artifacts (bizarrely my room had a set of English hunting prints on the walls - "Gone To Cover" and so on!) and the result indeed creates the impression of an ancient castle - all quite cosy and welcoming, even in winter.
I asked the receptionist how far it was to walk into Mataro itself , and she said it was about 1 Km but she made a face and suggested that it would not be very safe to do so in the dark. I took the hint and decided to eat in! The meal was perfectly OK but nothing special. Interestingly, this being a Saturday night, the restaurant was full of locals of a certain age all come for the dinner and the music and dancing which started at 11pm! This appeared to consist of a chap at an electric keyboard with an electronic beatbox, and fearing the worst I left before it started! I couldn't hear it at all in my room on the 3rd floor. Breakfast was again fairly basic.
The room was fine. The floor was tiled, but I was warm enough. The bed was a trifle too hard and the pillow too soft for my taste but such things are subjective. The bathroom was excellent - modern fittings, lots of marble (effect) and a plentiful supply of hot water.
All things considered the Castell De Mata was by no means a bad place to stay. I'm not sure about the safely of walking into the city in the dark. I didn't ask for details. There was no pavement, just the cycle lane to walk along so the receptionist might have meant that, but a few years ago I had the entire contents of my car stolen in broad daylight in Badelona, a few miles south, and she might have meant that walking would risk my personal safety. At least the route between the Ibis - also on the N11 but on the South side of town - and the historic centre of Mataro was all well lit by streetlamps, so if you want to walk into town for a meal that might be a better bet. But the Ibis would certainly lack the charm of the Castell De Mata. As usual - your choice!
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.