Near the property, you can find grocery stores, bakeries, pastry shops, clothes shops and even a small fair. There are also many shopping centers in Porto area. All have a big supermarket inside.

The Essential
Markets
On the Gaia side of Douro, the nearest supermarket is Jumbo in Arrábida Shopping Center. The other is Continente, in Gaia Shopping.
You have also small grocery stores near the flats like Mercado Portas Vermelhas on R. Cândido dos Reis 47, 4430-175 Gaia, about 350 meters from the apartment.
In front of the river, on weekends, there is a small fair where you can find all sorts of Portuguese souvenirs.
On Porto side, there are big supermarkets too, of course. But, instead, I’ll urge you to visit Bolhão, an old monumental market (picture on the left) where you can buy almost everything.

the accessories
Shops
The Shopping Centers in Porto and Gaia all have beautiful shops for every pocket.
You can find all the Portuguese and international brands on those shops. In Gaia, about a kilometer from the Flats, you have Arrábida Shopping the biggest on Gaia side of Douro.
Porto is known for its commerce streets, corners and squares. The most important is Santa Catarina, an old commerce street that has also a Shopping Center. But there are shops of all kinds everywhere in the city.
Downtown Porto (streets around Aliados Avenue, Cathedral, Ribeira, Boavista, Foz, and so on) there are small artisans shops’, antique shops, old book stores. And, of course, cloth stores, food stores, you name it! Take your time and wander throughout those streets and squares. You’ll be rewarded for sure.
If it is still not enough, you can visit others like Norte Shopping, Mar Shopping or, for those bargain lovers, Porto Fashion Outlet in Vila do Conde, 15 kms north of Porto.