Black truffles are among the most costly French delicacies and the world's most expensive mushrooms. If you are unsure whether the subterranean fungi are worth your money, head to the new truffle museum in France's south-western Périgord province, famous for its black truffles. Housed in a renovated town palace in Sarlat, the museum teaches you all you need to know about the region's "black diamonds" - and also lets you try them, according to French tourism agency Atout France. After learning ab