You ask "What is there to do in Lisbon"?
When I am in Lisbon, the first thing I do is to stroll down the Avenida Liberdade gazing at the tiles and designs of the sidewalks. I wander down to the Rossio after buying a Lisboa Card at the information center on Restauradores. (The card enables you to ride free on the Metro, buses, trams, elevators, trains,and enjoy discounts at many museums). Next I take in the Praca do Comercio and have lunch. After lunch I do some shopping. Then it's time to take trolley#28 up to the Alfama and visit the Castelo Sao Jorge, the Se (Cathedral), and St. Anthony of Padua's birthplace just south of the Se.
From the castle, you can view the Tagus River and the April 25th Bridge.
When I descend to the Praca do Comercio in Lisbon again I walk over to the Travessa Santo Antao for roasted chicken dinner. The Travessa is located just behind the Rossio and the it has many great outdoor restaurants.
On the way back up the Avenida Liberdade I stop at a kiosk for an expresso and enjoy sipping it as I watch the world go by in this wonderful capital city.
Tomorrow is another day when I will go up to the Bairro Alto on the Santa Just a Elevador and visit the Carmo museum where I will view the remains of the monastery which was ruined in the 1755 earthquake.
There is so much to see and do in Lisbon. I have traveled here many times and still have much to see.
Time to go back again.