A UNESCO World Heritage Site, the city of Porto displays an unparalleled mixture of old and new that at times might make you believe you're in Rome. With its narrow streets, Roman ruins and old town houses, Porto has also successfully managed to integrate the modern architecture. Situated on the hills at the mouth of the Douro river, this city boasts its mercantile past in the beautifully painted, crammed 2-stories river houses. The "tripeiros" (the locals of Porto) are welcoming people and always eager to show you around. This is the best place to sample the world-famous Oporto wine, but be advised: this ambrosia is strong and will literally sweep you off your feet. So better leave the car at the hotel if you're going to taste it!
And while on the subject of cars, it should be noted that although Porto proper only has a population of about 250,000 , nearly 2 million people live within about 50 km , divided in many smaller towns and villages, making it one of the densest places in this part of Europe and a delight best visited by car.