In which year was the world's oldest surviving railway tunnel completed?

The railway (railroad) tunnel predates the development of steam-hauled trains. The oldest surviving example in the world is the Fritchley Tunnel in Derbyshire, England. The tunnel was constructed in 1793 by Benjamin Outram as part of the Butterley Gangroad, originally a horse-operated railway linking the Cromford Canal with quarries at Crich.

With the coming of steam the Fritchley tunnel was altered in the 1840s and remained in use until the railway closed in 1933. It was sealed up in the 1980s and recently (2013) has been excavated by archaeologists. The tunnel has been scheduled as an ancient monument.