This apartment might be great for you, it just wasn't great for us. It depends what you're looking for in the place where you stay.
I will start with the positives:
- the host is very nice and welcoming
- the apartment is located in a building with cultural and historical significance
- the apartment is located on Passeig de Gracia, which is an excellent location, with easy access to everything
- the two balconies at the front of the apartment (towards the street) provide excellent views of the city
Here are the negatives, which I mention in my feedback because I believe they can be easily improved. Prior to my review all reviews have been 5 stars, and I assume no one has mentioned these issues before to the host. Also, maybe they didn't and won't matter to other guests, but they did matter to us:
- of the 4 bedrooms, 2 of them don't have windows, so you really need to turn the air conditioning on to have enough oxygen in the room during the night (if you're a smaller group and using only the 2 main bedrooms you'll be fine, but if you're a larger group and some people will need to sleep in the 2 smaller bedrooms it might be unpleasant for them) - the people who have to sleep in the small bedrooms would most likely be much happier with a hotel room
- the apartment has 3 bathrooms, however the water heater can't handle 3 different showers (it's from 2008 and has no storage tank) - we had to shower one at a time (so we wasted a lot of time in the morning waiting for everyone to be ready) and worst of all, the 4th or 5th person usually didn't have enough hot water left and either had to wait 10-15 more minutes for the water to heat up or use cold water (I think the water heater in the apartment should be changed with a new one, otherwise there's no point in having 3 different bathrooms and it's not great for larger groups)
- the pillows were terrible quality and we all slept quite poorly the first night - the second day we went to Zara Home right around the corner and purchased goose feather and down pillows for 20 EUR each and we slept much better (again, I think this is a very small investment for the host to upgrade to higher quality pillows)
- only one of the bedrooms in en-suite and has a full mattress, the second larger bedroom has two separate mattresses
- one of the sofas in the living room was smelly (dirty feet), but I think that could be solved with the help of a professional cleaning service to remove the smell
- one of the bathrooms had hairs on the walls next to the shower (cleaning of that bathroom could have been more thorough)
Again, this apartment might be great for you if you want to stay in a historic building, in an older apartment with cultural significance and be in an excellent location. In my opinion, it's not that great if you're looking for comfort in the bedrooms and bathrooms during your stay. Some of the issues I've mentioned are easily solvable and I hope the host will fix them.