Once the ice that cover majority of the European autonomous nation of Greenland vanishes, man will find many interesting features of its terrain and landscape. One, is the mega canyon of Greenland, far longer than the Grand Canyon of mainland United States of America.
According to NASA:
Data from a NASA airborne science mission reveals evidence of a large and previously unknown canyon hidden under a mile of Greenland ice. The canyon has the characteristics of a winding river channel and is at least 460 miles (750 kilometers) long, making it longer than the Grand Canyon. This immense feature is thought to predate the ice sheet that has covered Greenland for the last few million years.