HAIDRA, the ancient Ammadaera, a village on the frontier between Tunisia and Algeria, 2om. S.W. of Kalaa Djerda, the terminus of the railway from Tunis, and the loading point for the phosphates from the quarries of that name. The ruins of Am madaera, where a colony of veterans was established at the end of the 1st century, are here. There is a fine triumphal arch, con structed in honour of Septimius Severus, another smaller arch and a mausoleum. There is an imposing citadel of the Byzantine period and two or three churches.