The Grand Canyon Skywalk is a transparent horseshoe-shaped cantilever bridge and tourist attraction in Arizona near the Colorado River on the edge of a side canyon in the Grand Canyon West area of the main canyon. USGS topographic maps show the elevation at the Skywalk's location as 4,770 ft (1,450 m) and the elevation of the Colorado River in the base of the canyon as 1,160 ft (350 m), and they show that the height of the precisely vertical drop directly under the skywalk is between 500 ft (150 m) and 800 ft (240 m).

MS Allure of the Seas is an Oasis-class cruise ship owned and operated by Royal Caribbean International. The Oasis class are the largest passenger ships ever constructed, and Allure is 50 millimetres (2.0 in) longer than her sister ship Oasis of the Seas, though both were built to the same specifications. Designed under the name “Project Genesis”, she was ordered from Aker Finnyards in February 2006 and her construction began at the Perno shipyard, Turku, Finland, in February 2008. She was named in May 2008 after a contest was held to name her and her sister. The keel of Allure of the Seas was laid on 2 December 2008, shortly after the shipyard had been acquired by STX Europe.

What do you imagine when you look through a key hole? Do you imagine seeing a Wonderland with a sinister Queen of Heart ruling over a magical kingdom? Or you might imagine an eye staring back at you, if you’re a fan of horror movies. Least of all do you expect seeing a picturesque view of St. Peter’s Dome, perfectly framed by green hedges. Is it a lucky coincidence, or was it intended by the maker? We might never know. However, this became a curious sightseeing spot for many tourists who visit Rome. Thus, if you’re ever in the area of Priorato dei Cavalieri di Malta, be sure to peep into this key hole.