The  A 4  is a portuguese Motorway which runs from Matosinhos

Matosinhos

Matosinhos Municipality is located in Porto District, Portugal. The main city is Matosinhos. It is bordered to the south by the city of Porto and lies within the Greater Porto subregion. The municipality has a population of 168,451 in 10 parishes. Many people have recently moved from the...

 to Amarante, with a length of 63 km, where it narrows to become signed as the IP road of which, by now, forms a part,  IP4 .
The motorway leaves the metropolitan area of Porto

Porto

Porto , also known as Oporto in English, is the second largest city in Portugal and one of the major urban areas in the Iberian Peninsula. Its administrative limits include a population of 237,559 inhabitants distributed within 15 civil parishes...

, through the urban areas of Ermesinde

Ermesinde

Ermesinde is a Portuguese city located in the municipality of Valongo, 9 km northeast from Porto. It has a population of about 40,000 inhabitants and an area of about 7 km². This means that although being the smallest of the civil parishes in Valongo's municipality, it's the most highly...

, Valongo

Valongo

Valongo is a Portuguese municipality located in the District of Porto, the city population is 18,698, and the municipality is composed of 5 parishes, of which three are cities and has a total population of 97,814 inhabitants.The two most populous cities in the Valongo municipality are Ermesinde,...

, Paredes

Paredes, Portugal

Paredes is a city in Paredes Municipality in Portugal.The city of Paredes has about 12,654 inhabitants. It is incorporated in the civil parish of Castelões de Cepeda....

, Penafiel

Penafiel

Penafiel Municipality is located in Porto District in the North of Portugal.The municipal areas surrounding Penafiel City have a population of 71,801 and are made up of 38 parishes, comprising 212,82 km²....

, until arriving at the mountainous town of Amarante.
It is also known as one of the most dangerous motorways in the country, particularly the descent from Campo to Valongo

Valongo

Valongo is a Portuguese municipality located in the District of Porto, the city population is 18,698, and the municipality is composed of 5 parishes, of which three are cities and has a total population of 97,814 inhabitants.The two most populous cities in the Valongo municipality are Ermesinde,...

.