GATA, Sierra de, in Spain, a ridge of mountains between Leon and Estremadura, commencing east at the termination of the Peña Francia, and extending S.S.W. into Portugal, where it unites with the Serra de Estrella. Two branches nearly perpendicular to its axis shoot out from it; one north, forming the watershed between the Aqueda and the Coa; and the other south, between the Alagon and the Erjas. The main chain forms part of the watershed between the Tagus and the Duero or Douro. This entire chain is almost wholly composed of granite.