The hop on hop off City tour is very good to see the main sights of the city. But the problem is reconciling the waiting time at the points to make the connections. That's why I recommend that you always do the 2 complete routes without letting go of the bus and only then choose the places you want to explore more.

We took both bus trips - old town and castle tour - travel time per tour once 1 1/2 hours and once 2 hours. During the tour of the old town, the audio guide was in poor condition, the "phrase book/tape" could be heard simultaneously in English and - probably - Spanish via the headphones (available on the bus, disposable packaging) and was therefore difficult to understand. Everything worked on the 2nd trip. You often get stuck in traffic jams for a long time, which is why the tours take a long time. We - 2 people - got seats on the first bus arriving at the bus stop on both tours and didn't have to wait for the next bus.

It was good, but in hindsight, the red bus tour would have been better as there was a guide to greet you. The yellow bus was like a stampede to get on. Everyone fighting and pushing. I've seen scenes like this in third world countries, but not a developed city like Porto. The elderly were the worst. I thought they were meant to be setting an example for the rest of us? The driver could have travelled slower. There should have been an actual stand on the road designating where the stop is, otherwise you get a heard of cattle all running up to where the bus stops. Etiquette quite literally went out the window, it was survival of the fittest, kill or be killed. When you did get on the bus, there were tourists who put bags everywhere to say the seat was taken. Someone quite literally threw the bags off from the chair and said: "first come, first serve" and proceeded to sit down on said chairs. Fair play to them really. My partner sat on my lap until one became available. It is what it is.