After 100 years of being closed to the public, Palácio Baldaya (or Baldaya Palace) in Benfica, built in the 19th century, was restored and opened for the public in 2017.
This wonderful building with an interior romantic garden was repainted in a strong blue and has an incredible mural of D. Maria Joana Baldaya (the original owner) by artist Rui Ferreira on the facade.
Along with original architectural features, statues and fountains, this cultural and innovation center has exhibition and training rooms, a library, a coffee shop (currently closed), and a coworking space. It also is a venue for concerts, fairs, conferences and other events. You can always check their facebook page to see what’s happening.
Right now, every first Saturday of the month there’s a wonderful handicraft fair where you can find Portuguese artisans and products.
You can get there easier by bus (716, 746, 758), but if you don’t mind walking, it is relatively near Colégio Militar/Luz metro station (blue line).
If you’re interested in other city libraries with near open spaces, I strongly recommend Biblioteca Camões (Check the Biblioteca Camões article), Biblioteca Orlando Ribeiro in Telheiras (Check the Jardins de Telheiras article), and especially the beautiful Palácio Galveias (Municipal library) in Campo Pequeno.