Iron Gate, Rom. Porţile de Fier, Serbian Gvozdena Vrata, gorge of the Danube River, c.2 mi (3.2 km) long and c.550 ft (170 m) wide, on the Serbia-Romania border between Orşova and Drobeta-Turnu Severin. There the river narrows and swiftly flows through a gap between the Carpathian and Balkan mts. Iron Gate, formerly an obstacle to shipping, was cleared of rock obstructions in the 1860s; the Sip Canal (opened 1896) permits large river craft to get past the gorge. Iron Gate is the site of one of Europe's largest hydroelectric power dams. The joint Serbian-Montenegrin-Romanian project (opened 1971) improved river navigation by impounding a large lake and has a substantial electricity generating capacity.