"the tar tar pits"

Polyglot tautologies, where you name something for what is already is, are amazing:

"The River Avon, running through Shakespeare’s hometown Stratford-Upon-Avon, is another example. 'Avon' in an ancient Celtic language means 'river' – so the River Avon is more properly the River River. The La Brea Tar Pits manage to be redundant in two ways: La Brea is Spanish for 'the tar' – so the La Brea Tar Pits effectively mean 'the the tar tar pits.'"

Wiki has a handy list of them.