For centuries, the Douro at Porto was crossed by ferries and rafts. A regular passenger boat service operated from 1744, but permanent bridges were impossible: the river ran too fast, flooded too deep, and its gravel bed shifted too unpredictably for piers. For major events -- religious festivals, army movements -- temporary pontoon bridges were assembled from boats chained together across the current. The chronicler Fernao Lopes describes such a bridge in the 15th century, used by the army of King Ferdinand I to cross between Porto and Gaia. By 1809, the Ponte das Barcas was the city's only bridge. Designed by the architect Carlos Amarante, it was built to open in the middle for river traffic to pass -- a feature that would prove catastrophic.

The day before, Soult had written to the Bishop of Porto demanding no resistance and threatening violence if met. French troops probed the defensive lines stretching from the coastal fortress of Sao Francisco Xavier in the west to the parish of Campanha in the east. Their initial attacks failed. At six o'clock the next morning, the full assault began along the entire perimeter. The defenders crumbled section by section as panic spread. Soldiers and civilians alike funneled toward the only escape route -- the Ponte das Barcas leading south to Vila Nova de Gaia. The bridge was never designed for this. Thousands pressed onto a structure meant for orderly crossings, their combined weight pushing against the limits of ropes and timber and the boats beneath their feet.

Accounts differ on exactly how the bridge failed. Some historians believe the sheer weight of the crowd caused a partial structural collapse, plunging hundreds into the fast-flowing Douro. Others suggest that Portuguese soldiers deliberately opened the bridge's central section -- the gap designed for river traffic -- in an attempt to prevent the French from crossing, only to trap the civilians already on the bridge with nowhere to go. The crowd behind kept pushing. People fell into the open water, were trampled, or drowned in the current. By some accounts, those who survived the crossing at the end did so by walking across the bodies of the dead and drowning that filled the gaps in the shattered bridge. The Douro, which had always been Porto's lifeline, became a mass grave.

The dead were interred at the church of Sao Jose das Taipas, which became the central point of commemoration. A shrine known as the Altar of the Alminhas da Ponte -- the Altar of the Poor Souls of the Bridge -- was erected on the Ribeira waterfront near the disaster site. In 1897, the sculptor Jose Joaquim Teixeira Lopes cast a bronze relief that replaced the original shrine's artwork, giving permanent artistic form to the tragedy. At the Boavista Roundabout in northwest Porto, a 45-meter column commemorates Portuguese and British victory in the Peninsular War. Around its base, sculptures depict not only soldiers but civilians -- the people of Porto caught in the bridge disaster. On the 200th anniversary in 2009, President Anibal Cavaco Silva attended a ceremony and inaugurated a steel sculpture marking the exact points where the Ponte das Barcas cables were anchored to the Porto and Gaia riversides.