A tunnel-shaped megalithic tomb of Europe, characterized by a rectangular chamber with no separate entrance passage. The structure therefore resembles a megalithic corridor under an elongated mound, though sometimes they are cut in the rock. Gallery graves are frequently but not always found under long barrows; they may be subdivided (segmented) or have additional side chambers (transepted). They are sometimes associated with elaborate facades and forecourts. Local variants are distributed in Catalonia, France, the British Isles, northwards as far as Sweden, as well as in Sardinia and south Italy. Most of the tombs were built during the Neolithic period from the early 4th millennium BC on and were still in use during the Copper Age when Beaker pottery was introduced; the Sardinian examples belong to the full Bronze Age. Many contain multiple burials.