Perhaps the most famous tourist attraction in Gaia are the Port Wine Cellars, warehouses where the famous Port wine is stored. The Cellars are placed in Ribeira de Gaia, an area of the city located in the bank of River Douro opposite Porto. Ribeira de Gaia has also some typical and international restaurants, particularly in Cais de Gaia. Even if you are not in visiting the cellars, you should visit Ribeira the Gaia in order to get some amazing views of Porto.
Small Nature Reserve for the Protection of Birds, (Begin at the base of the Dom Luis I bridge and head down river about 5.3 km. The journey is easy but not particularly interesting.), . edit
Bike (or walk) to the Atlantic coast, (Begin at the base of the Dom Luis I bridge). Head down river 3.7 km to the marina. The journey is easy, but not particularly interesting. When you reach the marina there may be some photo opportunities with local fishing men and laundry women. Continue about 1.6 km to the nature reserve for bird watching at the estuary. Continue on from there to begin access to the path that runs south along the Atlantic Coast another 15 km to Espinho. edit