Nobody "discovered" Stonehenge; since its construction, the existence of the monument is likely to have been known. The earliest written references to it are found in "Historia Anglorum" by Henry Huntington and "History of the Kings of Britain" by Geoffrey of Monmouth, both written in the 12th century.
Researchers have more recently made new discoveries about Stonehenge. In 2014, for instance, it was revealed that Stonehenge was originally larger and stood as a complete circle of standing stones.
Older structures at the site, which predate Stonehenge by 400 years, have also been discovered with modern technology. These include two pits within a monument called the Cursus, which lies to the north. The pits form astronomical alignments and intersect at a point.