On board Porto's number 1 tram. This tram route runs along the northern bank of the Douro from downtown Porto to the Foz district. It's a great way to take in a few sights, such as the Arrabida bridge and enjoy a little history - these trams date back to the 1930s and have changed little.
The fare is actually quite pricey if you just buy a ticket on the the tram. However, it becomes fairly inexpensive if you have a travel card - which is why you still see some locals on here outside of peak tourist times.