On Areos street, just opposite the entrance to the Monastiraki metro station, lies the archaeological site of Hadrian’s Library. Though only a few remnants remain intact, many other valuable findings are being unearthed in this ongoing excavation. Described in written detail by Pausanias the traveller in the 2nd century A.C., the Library was comprised of 100 columns, supporting a gilded roof, and was decorated with precious alabaster artifacts.
Today the visitor can see the pediments of the internal yard columns, the four, seven-meter-long forming alleys, the foundations, some two-story walls near the southern perimeter, remnants of a pavilion in the centre of the yard, and, to the north-west, the Library entrance, framed by seven Corinthian era columns. The entrance to the site is on Areos street., opposite the exit of the Monastiraki Metro station.
Source: www.athensattica.gr