Climb of the Clerigos Tower:
The climb up is a bit tiring and involves narrow, claustrophobic hallways lined with steep steps (openings along the way so you don't feel closed in). 206 steps. On the way up to the top you get a close-up view of the mighty bells that hang within the tower. The scenery at the very top is breathtaking, with a 360 degrees view of Porto, the Douro river below and the Igreja dos Clerigos church adjacent to the tower.
€3 euros - adult, €2 - senior or student.
Tip: Go there late afternoon and watch the sunset - unforgettable experience !
Warning: In case there are a lot of people it will take you some time to climb it (the stairs are very narrow). Worse than that: the top balcony can be full and heavily packed (like in the Vatican St. Peter Basilica Dome).