How long was the golf hole that Adam Rolston created and played in Mongolia?

1,850 km (1,150 mi) which took 82 days, par 14,000.

In 2017, Adam Rolston (a scratch golfer) along with caddy Ron Rutland undertook this venture with a view to setting a record for the longest golf hole. Rolston was hitting 160-180 shots each day on the flat Mongolian desert. The duo also had to take 400 spare golf balls, a weight of 25-30 kg.

“We’re taking a putter the whole way just to finish off at that one moment – a bit of useless kit we’re going to carry for 82 days.”

https://www.cnn.com/2017/08/16/golf/longest-hole-of-golf-mongolia/index.html