Porto is the second largest city in Portugal after Lisbon . It (1)...is... one of the major urban areas of the Iberian Peninsula.Located along the Douro river estuary in Northem Portugal. Porto is oen of the oldest European centres. (2) ...In..... 1996 ,UNESCO reognised its historic centre as a Word Heritage Site .Among the architectural highlights of the city . Porto Cathedral is (3)...the.... oldest surviving structure .It attracts millions (4).......of.... tourists every year