[jcranmer]

In the interests of being pedantic, the slice of Antarctica that no one has any claims in is the largest expanse of unclaimed land on Earth, and it has the advantage of being actually unclaimed.

Bir Tawil and the Danube pockets are claimed, it's just that the border disputes mean that both parties argue it's the other side's claim; should the border dispute get resolved, there will be a clear owner of the land.