The world's highest measured sand dunes are those in the Saharan sand sea of Isaouane-n-Tifernine in east-central Algeria. They have a wavelength of 5 km (3 miles) and attain a height of 465 m (1,526 ft).
The Sahara is the largest desert in the world.
In China's Badain Jaran Desert the dunes are reported to reach 1640 feet. The tallest dunes in the Sahara Desert are around 1500 feet, and in the Namibian Desert they grow to around 1200 feet.
The sand dunes of Mars are several times larger than Earth dunes.