The Ajuda National Palace is in a remote area of central Lisbon, so you have to take a bus/tram to get there. Admission is € 5, but with a student card it's free, on Sunday morning it's also free. The palace is beautiful, both outside and inside, with some furniture, ceilings, lamps - precious. I loved it. To complete the look, you can see the Ajuda Botanical Garden, which is right across the street from behind the palace.
Belem Palace is the official residence of the president (since 1911) after the proclamation of the republic. It's opposite the Praça Afonso de Albuquerque, which commemorates the first Portuguese Viceroy of the Indies. A column that has reliefs on the neomanuelina pedestal that tell the life of the viceroy is in the square. In the shade of the trees that pervades this beautiful park we rested a while from the busy day and prepared, via information from from Internet, the place where we were to recover from the day.
By taking the tram 28 toward the Barrio de la Estrella, you will reach this remarkable building that houses the Portuguese Parliament. It gets it's name from the Benedictine convent that is is built upon.