The double-deck iron arch bridge spanning the Douro gorge is Porto's great civic symbol, and crossing it at the upper level — on foot or on the metro — is one of the city's essential experiences. At 45 metres above the river, the upper deck places you level with the terraces of Porto on one side and the cellars of Vila Nova de Gaia on the other, with a view downriver to the Atlantic and upriver into the canyon that hints at the Douro Valley beyond.
The lower deck, a few metres above the water, connects the Ribeira neighbourhood on the Porto side to the port wine lodges along the Gaia embankment. Walking across either level is free (the metro charges its normal fare). The classic photography position is from the Monastery of Serra do Pilar on the Gaia side, looking back across the river at Porto — the view that appears on every postcard. But the view from the bridge itself, with the city climbing the hillsides in every direction, is better.