You might only have heard about the place in the U.S. referred to as Area 51. In fact, it is a popular location mentioned in Sci-Fi movies of Hollywood, preferably about alien conspiracies. However, such claims about aliens around Area 51 have been demystified.
The location is now confirmed to be a historic ground for testing military aircraft, including the SR-71 Blackbird, U-2 Spy Plane, and the stealth fighter jet F-117A Nighthawk.
However, if you look at the popular Timelapse feature of Google Earth, you would notice that the area has developed over the years since 1984. In fact, this was initiated by the U.S. Military since the first photograph was captured.
For this reason, it can be said the United States government has invested a lot for the construction of the base, particularly the North end of the site. Moreover, it can be observed that military engineers were digging steadily into the mountain towards the West part of the base.
If you can see from the Google Earth satellite images, this excavation site has expanded over the decades. Nevertheless, its purpose might be unknown to many people.
Take note that this military base observes 37km x 40km of no-fly zone for any civilian aircraft. So, you can say that this area is basically off-limits for public viewing. The only thing that you can do is to view it via satellite feed from space, which the U.S. government is not bound to block.
By using the Timelapse feature of Google Earth, you can experience different changes to the surface of the planet. In fact, you can see a lot of improvements in the number of years added to the imagery, providing new data, with a much clearer view of the world over the past 32 years.