I stayed in Lisbon for 5 days, so I redeemed and used the 72-hour Lisbon Card at the tourist office. It turned out to be an excellent decision! Not only did it grant free admission to major attractions like Jerónimos Monastery, Belém Tower, and São Jorge Castle, but it also offered unlimited rides on the subway, trams, and funiculars. Lisbon has a lot of hills, so being able to easily hop on a tram or elevator even for short distances was a huge help physically. I used one of the three days for a day trip to Sintra, and since the round-trip fare for CP (the national railway) was also included for free, I think it offers incredible value for money. The system of counting 72 hours from the 'time of first use' rather than by date was also efficient and prevented any waste. I definitely recommend it if you plan to explore Lisbon thoroughly!