An earth oven or cooking pit is one of the most simple and long-used cooking structures. At its simplest, an earth oven is simply a pit in the ground used to trap heat and bake or steam food. Earth ovens have been used in many places and cultures in the past, and the presence of such cooking pits is a key sign of human settlement often sought by archaeologists, and remain a common tool for cooking large quantities of food where no equipment is available.To bake food, the fire is built, then allowed to burn down to a smolder, and the food is placed in the oven and covered (this can be used for bread-baking, for example, and has been used in some cultures for soldiers on military expeditions). Steaming is similar; fire-heated rocks in a pit are covered with green vegetation, large quantities of food, more green vegetation (and sometimes water), and then a final covering of earth. Food takes several hours to cook whether by dry or wet methods.Today, many communities still use cooking pits, at least for ceremonial or celebratory occasions: the Hawaiian luau, Māori hāngi and the New England clam bake. The central Asian tandoor, used primarily for uncovered, live-fire baking, is a transitional design between the earth oven and the horizontal-plan masonry oven, essentially a permanent earth oven made out of clay or firebrick with a constantly burning, very hot fire in the bottom. In modern times, earth ovens are sometimes used for outdoor cooking and recreational meals in lieu of an open campfire.