On a budget, weigh it — Parque das Nações isn't cheap for what it is.
Free (attractions priced separately)
A complete tonal break from old Lisbon: wide clean waterfront promenades, a gondola over the river, fountains and family-friendly space. The catch: it's deliberately corporate-modern and can feel sterile or empty off-peak, and it's far east. Great with kids or for a riverside stroll; skip if you only have a day for the historic core.