Filopappou hill or Filopappou monument or just Filopappou is named a hill really close to Acropolis.
You can reach Filopappou by following the Areopagitou pedestrian from Plaka and then turn left towards Pnyx, following Pikionis Pathway. Pnyx is on your right, Filopappou is on your left.
On the top of the hill there is a burial monument, dedicated to a Roman prince, from the ancient Kingdom of Commagene. His name was Γάιος Ιούλιος Αντίοχος Επιφανής Φιλόπαππος or in English Gaius Julius Antiochus Epiphanes Philopapous (probably meaning friend of the grandparents, since -pappou is the grandpa in Greek).
The alternative name of the Hill is Mouseon or Muson Hill, named not after the nine muses, but after Museos, a mythical musician-poet related to legendary Orpheus. After Philopapous’ death, the monument was erected (during 2nd century AD) on the top of the hill, as a tribute and mausoleum, even though due to the mythical connection to Museos, the hill was considered as sacred.
What you can do from there
The hill was excavated at the 19th century. Today besides the Monument, at the south side of the hill, there is Dora Stratou theater, where Greek traditional dances show take place during summer. From Filopappou you can walk to Koukaki and Petralona areas.
From the hill you can easily access NOA hill or Asteroskopeio or Observatory or Nymph Hill, and of course Pnyx. At the other side of the hill there is Socrates’ prison.
Also you can follow Pikionis pathway– a remarkable construction at the hill and follow the traces of the ancient city walls and more. You can go to Pnyx, passing from Loumpardiaris church, another astonishing temple of Athens.