In 1997, a mysterious steel door appeared set into the cliff between Waiake beach and Browns Bay (Auckland, NZ). I remember the the local papers discussing the occurrence, and eventually it was determined that the owner of the house at the top of the cliff had used an engineering firm to secretly construct a tunnel down to the beach. Apparently, it was a substantial effort, and was allegedly constructed on the site of a much earlier tunnel.
It is certainly well built, particularly the door and locking mechanism itself, as you will see shortly. Because a couple of years ago I saw an opportunity to gain access to the tunnel; in a non-damaging way, or course. The handheld camera at night lead to some shaky photos. The wooden staircase itself goes up for several stories.
One of the stories at the time related to the former owner (not the current owner) chasing someone away from the door by waving a crowbar and squirting them with a hose; keep an eye out for these items in the photos below.