Lisbon can be an intense city and if you want to see it all at once, you will need a break.
For example, if you are exploring Parque Eduardo VII, visiting Jardim Amália Rodrigues or even shopping at El Corte Inglés you must go to Linha D’Água.
It is a the perfect place to rest after some of those activities or even for a fresh, quality light meal. They also have a great selection of ice teas and natural juices.
The water surrounding the area makes this place very peaceful and relaxing. You should sit outside, in front of the fountain, and just breathe. You can also enjoy the view while reading a book and be surprised by how quiet it can be in Lisbon.
You can also sit on the grass, enjoy some of the sunniest days in the city, hear the birds and feed the ducks that live in the lake nearby. They will steal your food if you’re not paying attention.
This was one of my favourite spots to study during college; many people are still going there solo with their laptops/books and doing some work/study (there is also free wifi so you can do some research about Lisbon’s main attractions).