Largest continuous sand desert

Covering an approximate area of 560,000 square kilometres (216,217 square miles), the Rub' al Khali ("Empty Quarter") sand sea – or "erg" – is not just the largest portion of the Arabian Desert, but also the largest contiguous area of sandy desert on Earth. Rub' al Khali is predominantly (about 80%) located in Saudi Arabia, but also spills over into adjacent areas of Oman, Yemen and the United Arab Emirates. Its expanse is equivalent to more than twice the total area of the UK and almost five times that of the US state of Arizona.

Some estimates put the area of Rub' al Khali at as much as 650,000 square kilometres (251,000 square miles), which is about the size of France; it's difficult to assess precise boundaries because it abuts other deserts in the region.

The Rub' al Khali desert contains large sand dunes – up to 250 metres (820 feet) high – and vast valley floors, interspersed with ephemeral bodies of water.