In the villages of the Minho, north of Porto, flax was once grown, retted, spun and woven at home, and a bride's trousseau of linen sheets and towels could take years to complete. The custom left one of Portugal's most recognisable textiles: the lenço dos namorados, the embroidered "sweetheart's handkerchief" that a young woman stitched with verses and gave to the man she hoped to marry, traditionally worked on linen or cotton. Porto, the commercial capital of that region, has always been where such things were traded.

The city itself is built of granite. Its houses climb the steep north bank of the Douro in tiers of grey stone, tiled façades and wrought-iron balconies, from the Ribeira waterfront, a UNESCO World Heritage site, up to the cathedral and the Torre dos Clérigos. The climate is milder and damper than Lisbon's: warm summers that rarely turn fierce, with Atlantic fog that can roll up the river in the morning and burn off by noon.

Those mornings ask for a shirt with some substance. The Bliss Linen Shirt in Grey, long sleeved, suits the grey stone and the cool start, and loosens comfortably as the day warms. It is part of the PP linen shirts collection, alongside the Male Linen Shirt in Grey, which offers the same colour in a more casual register. PP Casual Linen Trousers in Black complete a palette that belongs in a granite city.

Across the double-decked Dom Luís I bridge lies Vila Nova de Gaia, where the port wine lodges keep their barrels in cool, dark cellars along the riverbank. A tasting tour moves from the warmth of the quayside into stone cellars that stay cold all year, and back. A long-sleeved shirt with the sleeves turned back, unrolled in the cellar, handles both. The Douro valley, where the wine is grown on terraced slopes upriver, has its own page in what to wear in the Douro Valley.

For women, the HER Male Linen Shirt in Pink, worn loose over pale trousers, carries a day of walking between the São Bento station, with its great panels of blue azulejos, and the cafés of Rua de Santa Catarina. The Amelia linen dress shirt in Blue belongs to an evening in Foz do Douro, where the river meets the ocean and the old seaside quarter has some of the city's finest restaurants. Both are in the women's linen collection.

Foz is also where the city goes to see the sea. The esplanade runs along the Atlantic towards Matosinhos, famous for its grilled fish, and the beaches are wide and windy. The water is cold; a swim here is brief and invigorating, and PP natural swim shorts are the garment for it. Shirts and linen shorts stay on the sand and the terrace.

Belgium shares this northern relationship with flax. The fields of Flanders and northern France still produce much of the world's long-fibre flax, and the certified Belgian linen at the core of the PP collection is traced from those fields to the woven cloth. The story of where the finest fibre grows is told in where the world's finest linen comes from. For the city wardrobe in full, see what to wear in Porto.

Read more: Linen in Portugal  ·  How Linen Is Made