Horn of Africa covered the Simien and Bale Mountains but melted at the beginning of the Holocene. The mountains descend in a huge escarpment to the Red Sea and more steadily to the Indian Ocean. Socotra is a small island in the Indian Ocean off the coast of Somalia. Its size is 3,600 km (1,390 sq mi) and it is a territory of Yemen. The lowlands of the Horn are generally arid in spite of their proximity to the equator. This is because the winds of the tropical monsoons that give seasonal rains to the Sahel and the Sudan blow from the west.
Gates of horn and ivory that of horn as the passageway for true shadows and that of ivory as that through which the Manes in the underworld send false dreams up to the living. Through the latter gate Virgil makes his hero Aeneas, accompanied by the Cumaean Sibyl, return from his visit to the underworld, where he has met, among others, his dead father Anchises: Two gates the silent house of Sleep adorn; <br>Of polish'd ivory this, that of transparent horn: <br>True visions thro' transparent horn arise; <br>Thro' polish'd ivory pass deluding lies. <br>Of various things discoursing as he pass'd, <br>Anchises hither bends his steps