The cheapest and easiest way to get from Porto airport into the centre of Porto is by the sleek, modern Porto Metro system. The great thing about this journey is that it is overground for the majority of time, giving you a chance to see parts of Porto you would not normally see. The Metro station is located just outside the airport terminal and is served by Metro E (the purple line). The trains start and finish here, so you don’t have to worry about getting on the wrong train or being on the wrong platform. Trains run every 30 minutes and the journey into the centre of Porto takes 30 minutes.Tickets are bought from the automatic machines at the entrance to the station. Before buying a ticket you need to check which zone you will be travelling to; all the stations are listed on the ticket machine and next to each station is a zone number, for example, Campanhã is listed as being in zone 4 (z4). Once you have found which zone you are travelling to, the instructions on the ticket machine screen are self-explanatory. The ticket you will buy will be the Andante Azul card, which is similar to the Viva Viagem card that is used on the Metro (and other public transport) in Lisbon, however, it is a bit more complicated than the Lisbon system. Like the Lisbon Viva Viagem card, the Andante Azul card is rechargable, so you will be charged 60 cents for the card when you buy it. What makes it more complicated than the Viva Viagem card is that you can only put journeys on the card for one zone at a time. You can only change zones when the card is empty. When you first arrive, I suggest you just buy a one-way journey on the card, which to the centre of Porto will cost around €1.95. Once you know how you intend to use it you can add more journeys to it in the correct zone. You will need to buy a different card for each person in your group and each card needs to be validated by holding it against the black circle on the yellow validation machine before you go up the steps to the platform. You also have to validate it if you change lines during the journey. More information can be found on the Metro do Porto website. A further tip is to carry some coins for the ticket machines, as they often have problems accepting notes.