When it comes to deserts, the largest one, the Sahara, is typically the one to capture everyone's imagination. There are, of course, some others- Gobi, Atacama, Mojave, Kalahari, the Outback- and of course you have your occasional wiseass who likes to remind everyone how a 'desert' just means a lack of precipitation as an excuse to toss in somewhere like Greenland. But one of the most forboding deserts is really more of a subset of the larger Arabian Desert that encompasses the Middle East: the Rub' al Khali, or Empty Quarter, which makes up southeastern Saudi Arabia as well as much of Oman, Yemen and the UAE. The Empty Quarter is the largest pure sand desert on Earth- the largest desert, that is, that meets the description of 'desert' that a small child would have. Every larger desert is going to have rocks and cliffs and such; here, we are talking nothing but sand the whole way.
And that makes it magnitudes harder to, oh, say, cross. Of course you can drive across it; 1,000 kilometers isn't exactly the Dakar Rally- heck, it's not even the Baja 1000, where spectators like to construct homemade booby-traps and put them on the course- and Dakar veteran Moi Torrallardona of Spain recently set a new record time crossing the Empty Quarter, managing 849 kilometers of it in 10 hours, 22 minutes.
It's walking it that's the problem. You have to work just to find a water hole, and that's all you'll find, apart from some occasional shrubbery. No settlements for the vast majority of the quarter (though ask the UAE about the roads and luxury resorts sometime that have relegated that section of the crossing to little more than hiking on the side of the freeway). No shade. Most of the time, not even a decent footing. That car you're driving can still easily sink into the sand. And sink. And sink. A lot.
For those of you who never played Uncharted 3, here is footage of a plane landing at an airport situated in the Empty Quarter. You'll get the basic idea.
The first non-local to cross it- first European, really- was Bertram Thomas of the UK in 1931, going from Muscat to Doha two years after Lawrence of Arabia himself mocked the very idea of it. Thomas had the aid of local guides, but they were guides who were kept in the dark about what in blue hell Thomas had gotten it into his head to attempt because otherwise they'd never have agreed to it. The Saudi segment of the desert is still as nasty as advertised, though the experiences of previous explorers means people attempting the crossing nowadays don't have to do like Thomas did and negotiate for three days to get guides and lead a whole entire expedition and look over the horizon for potential enemies of the guides. You still, though, have to bring everything you're going to be using. No living off the land, like you could try to do in expeditions elsewhere.
Until you get to the UAE. Then you just flag down the first person willing to drive you to Dubai.