The name of this square, which could be translated as "little monastery", comes from the church situated there. Nowadays, not only the square but also the surrounding area is known as Monastiraki. This district serves as a popular shopping destination, with a variety of shops as well as dining facilities. If looking for a unique souvenir, you should not miss visiting a flea market located only a short walk from the square.
Wikipedia https://en.wikipedia.org/wiki/Monastiraki
Address 4 Πλατεία Μοναστηρακίου, Αθήνα 10555, Greece
Coordinates 37°58'34.995" N 23°43'33.32" E