Lisbon rewards walking and punishes it at the same time. The city is built across seven hills of small, slippery limestone cobbles, which means a map distance of one kilometre can involve a forty-metre climb. Plan fewer things per day than you think you need, and take the funiculars without guilt.
Almost everything worth doing inside the city you can do yourself for free. The paid activities that earn their money here are the ones solving a specific logistical problem: getting to Sintra without losing half the day to shuttle queues, getting into Pena Palace without a timed ticket you forgot to buy, or getting onto the river, which you cannot do alone.
Where to spend your money
Book: the Sintra day trip, one food tour on your first night, and a sunset sail. Those three cover the things that are hard or impossible to arrange yourself, and together they cost less than a single day of a package tour.
Skip: hop-on hop-off buses, which move slower than the metro and cannot climb into the neighbourhoods you want to see. Also skip anything advertising a "fado dinner show" with a set menu — real fado happens in small Alfama houses after 9pm, and the good tours take you to one.
The part nobody tells you
Lisbon's museums and monuments close on Mondays, almost universally. Belem Tower, Jeronimos Monastery, the Gulbenkian and the Tile Museum all shut. If your trip includes a Monday, that is your Sintra day or your beach day — not your museum day.
