The old Lisbon offers so many awesome places, charming corners, observations points ("miradouros"), meandering narrow cobbled streets in Alfama and Mouraria or statelly squares in Baixa and Chiado, but Calçada (staircase passage) do Duque is really one of our favorite places in the entire city.
Its lowest point is located right by the city's 2 most central squares, the historic Rossio (officially named Praça Dom Pedro IV) and newer Praça dos Restauradores, next to Rossio train station. As a matter of fact, you can get to the beginning of Calçada do Duque from the upper level of Rossio train station, thus saving 2 extra flights of stairs by the Calçada do Carmo. Calçada do Duque's end, or its highest point, opens to Largo Trindade Coelho, with its historic Igreja (Church) and Museu (Museum) de São Roque, plus gets you right on the juncture between Rua de São Pedro de Alcântara to the north (ultimately leading you to Bairro Alto "partying" neighborhood) and Rua da Misericórdia to the south, a straight route to Praça Luís de Camões, most major points in Chiado and down Rua do Alecrim with its "Pink Street" at the end, and the famous TimeOut Market.
Sure enough, there are alternative ways to get to all of the above, requiring less steep climbing and less physical efforts, but Calçada do Duque offers unparalleled views to Rossio Square, parts of Baixa, with the old neighborhoods of Alfama and Mouraria further east, in the background.
Climbing up, Calçada do Duque opens on three streets, Rua do Duque, Rua da Condessa, and Rua da Oliveira ao Carmo, all of them ending by Largo do Carmo, with its Convento do Carmo, one of the very few buildings remaining, even if partially, from the pre-1775, pre-earthquake Lisbon.
Climbing up there are more than a few restaurants and bars, all of them on the left side of the stairway, however, those are not known by its high quality neither authenticity, but are by and large those "laminated menus" joints, with the servers standing by the doors, trying to get you inside, those kind of places.
Highly recommended for amazing views and efficient shortcut to various points of old Lisbon.