I have tried so many Pasteis Nata but this is still my favourite place. 

Fish, fish, fish. The crab is amazing. You get a hammer and hammer your way through delicious fish meat. The famous fish restaurant 'Ramiro' is a couple hundred meters down the street. It has lines for hours, not worth it! Walk up to this one with no line, half of the price and frankly better food as they don't need to rush.

In the very touristic Graça area, there is this heaven place, hidden from tourists. This café belongs to the theater da Garagem. It has an amazing view, the atmosphere is peaceful and with a lot of light. They don't have wifi if you plan to work there though..

Flea Market. Tuesdays and Saturdays.

There are not many full of green parks in lisbon, this is a quiet botanical garden that i usually go to read a book and be around dark green plants.