Palau Robert is a cultural centre in the middle of the city, where Diagonal and Passeig de Gracia meet. Behind the building there is a little park, and since I live very close to it I pass through it almost daily.
The park is an oasis in the middle of the city chaos. Inside you barely hear, or at least barely notice, the sound of the traffic outside. Bring a book, sit down on the bench and the stress will slowly disappear.
My favourite time in the park is when the orange trees have flowers, and it smells enchanting. There are still months to go until that unfortunately, but now the orange trees are full of fruit.