For a few years, the Lisbon City Council has been encouraging cycling and 6 cycle tracks have been created. I tested the track that runs along the Tagus from Oriente to Belém.
The first time I arrived in Belém I was immediately charmed by the wide open spaces, a magnificent walk along the Tagus, the proximity to the ocean, the impressive 25th of April bridge and the magnificent modern or historical buildings up to the Tower of Belém, the change of scenery is total. The opportunity to cycle through this part of the city is more than tempting.
August 2020, on holiday in Lisbon I decide to do the Sacavém - Algeciras cycle path. The day before I downloaded the application Gira the Lisbon Velib. I strongly advise against using Gira unless you want to spend your time calling Gira support as the app does not work well at all.
I advise you to rent a bike directly from a bike rental shop to avoid any surprises and to have a guaranteed price for the day.
The big problem I had with Gira is that all the stations to return the bike in Belém are out of order, plus the fact that the application doesn't work very well as I already told you, so I don't recommend you to use Gira. There are many rental companies all over the city.
The route is beautiful, count half a day for a quiet ride.