The 7 hills, on which the city rests, have several viewpoints that allow a joint view of the city and the Tagus river.
Several suggestions are presented by the Lisbon City Council and other entities. See all schedule at Agendalx.
Information on city spaces to visit by theme and parish
Tourist tours in Lisbon with Yellow Bus Sightseeing Tours. Panoramic hop on hop off bus, tram and boat.
Visit the website of the Lisbon Tourism Association and find out their suggestions for visits.
See also information that may interest you about sightseeing.