sentences:  There have been recent discoveries (2010–2011) of Hypogea (structures carved into embankments, that may have been used for burials) on the islands of Corvo, Santa Maria and Terceira, that might allude to a human presence on the islands before the Portuguese.There is no clear evidence that there were, in fact, other inhabitants on the islands, and archaeological investigations are only now commencing as to the age and relevance of these structures.The Azores archipelago began to appear on portolan charts during the 14th century, well before its official discovery date.