The Douro's six crossing points — Arrábida, Freixo, São João, Maria Pia, Infante Dom Henrique, and Luís I — span 134 years of Portuguese engineering, from Théophile Seyrig's 1877 wrought-iron Maria Pia railway viaduct to Edgar Cardoso's 1963 reinforced-concrete Arrábida arch. Luís I, completed in 1886 by Seyrig's atelier, carries pedestrians on its upper deck 45 metres above the waterline, linking Porto's Ribeira quarter to Vila Nova de Gaia's port wine lodges. The six structures form a visual chronology of bridge-building: masonry piers give way to lattice ironwork, then to pre-stressed concrete and orthotropic steel decks. Each design responded to the Douro's tidal fluctuations and the city's vertical topography. Traditional rabelo boats — flat-bottomed oak barrels that once hauled port wine casks downriver from the Douro Valley quintas — now operate as passenger vessels. Their low freeboard and shallow draft let them pass beneath the bridges' lower chords, offering sightlines inaccessible from the quayside. The cruises depart from Cais da Ribeira, the medieval waterfront where 18th-century warehouses have been converted into cafés and terraced restaurants. Most 6 bridges Douro river cruise Porto tours follow a westbound route to the Arrábida bridge, then return upstream past the clustered spans of the city centre. The riverfront panorama includes the Clérigos Tower's 76-metre baroque campanile, the granite façade of the Palácio da Bolsa, and the tiered Ribeira houses painted in ochre and terracotta. The Douro here is a working estuary: container ships and fishing trawlers share the channel with tour boats. The Maria Pia bridge, decommissioned in 1991, remains a monument to 19th-century railway expansion, its parabolic arch echoing the design Gustave Eiffel later employed on the Garabit Viaduct. The six bridges Douro river cruise Porto experience condenses a century of urban infrastructure into a 50-minute upstream-and-return voyage, each span marking a chapter in the city's relationship with its defining river.