The Thrasyllus monument was erected by Thrasyllos in 320/19 B.C., high on the south slope of the Acropolis, on the rock which had been evened out vertically during the construction of the Dionysos Theater.
This is classified as a choragic monument, the choragos being the patron who paid for and supervised the training of the dramatic dance-chorus.
Texts and images sources: https://www.wikipedia.org/, https://www.visitgreece.gr/