It was designated a World Heritage Site by UNESCO in 1986 .
A 3 - mile ( 4.8 km ) stretch of the River Severn in Shropshire , is known as Ironbridge Gorge .
River Severn was designated a World Heritage Site by UNESCO in 1986 .
A 3 - mile ( 4.8 km ) stretch of the River Severn in Shropshire , is known as Ironbridge Gorge .