After its initial use, Newgrange was sealed for several millennia. It continued to feature in Irish mythology and folklore, in which it is said to be a dwelling of the deities, particularly The Dagda and his son Aengus. Antiquarians first began its study in the seventeenth century, and archaeological excavations took place at the site in the years that followed. Archaeologist Michael J. O'Kelly led the most extensive of these and also reconstructed the frontage of the site from 1962–1975, a reconstruction that is controversial and disputed. Newgrange is a popular tourist site and, according to the archaeologist Colin Renfrew, is "unhesitatingly regarded by the prehistorian as the great national monument of Ireland" and as one of the most important megalithic structures in Europe.