Porto is the second largest city in Portugal, located at the mouth of the Douro River in the northern part of the country. The old town, located on the Ribeira pier, is the most important part of Porto and its main tourist attraction. The old town is situated on the granite Penaventosa hill, on the northern bank of the Douro River. There are six bridges over the river that connect right and left-bank part of the city. The oldest buildings in the centre of Porto come from the Middle Ages, the youngest - such as Casa da Musica - from 20th century. The old town in Porto is listed on the UNESCO World Heritage Site List.