The Sanctuary consisted of :
Theatre : It is dated at the end of the 3rd c. B.C. or the beginning of the 2nd c. B.C. and was built for the needs of the musical and theatrical games which were held in the Valley during the festival of the 'Mouseia' devoted to the 9 Muses. Spectators sat on the seats cut in the mountain slope. Only the first row - the prohedria - was marble. Nowadays preserved are the 'skene' and the 'proskenion'.
Long ionic stoa (length 96,70 m.) on the west of the small temple which housed the votive offerings to the Muses. It is dated in the 3rd c. B.C. Originally it had an internal wall and rooms; the former was replaced later by collonade in the Corinthian order.
Small temple or altar of the Muses: It is a small rectangular building dated in the same time-period as the theatre and the stoa, in 3rd c. B.C. It was revealed after the demolition of the church of Ayia Triada which had been built upon the ancint foundations.
Bases of the statues of the Muses: During the excavations there were found 9 bases of the statues which originally stood in a single group. On 5 of them - on the most well preserved - were inscribed names of Muses and epigramms, works of the poet and sculptor Onestos.
The square tower of Askra of the 4th c. B.C. which crowned the hill Pyrgaki and dominated the Valley from the N. It had 3 store-rooms on the ground floor. Earlier circuit wall, now ruined, enclosed the tower. It was probably built by the Thespian a little before 371 B.C. ( battle of Leuktra ) to control the movements of the Thebans.
The history of the famous Valley of the Muses on the eastern slopes of Mt. Helikon began in the 6th c. B.C. Its floruit period began from the 3rd c. B.C. onwards because of the 'Mouseia', festivals established and oganised every 5 years by the Thespians. Poets and musicians from all over Greece also participated in various games (epic, poetry, rapsodia, kithara, aulos, satyric poetry, tragedy and comedy). In the 2nd and 1st c. B.C. were also added in the list game in honour of the roman emperor who from that time sponsored the whole organisation. The festivals were called onwards 'Great Kaisareia' because the emperor was honored at first place and not the Muses. The winners dedicated their tripods to the sanctuay. Hesiod did the same after his victory in Chalkis. Many statues depicting the Muses, famous poets and musicians stood in the open-air space of the Valley.
In 1882 A. Stamatakis made the first test trench in the little church of Ayia Triada and noted the rectangular foundation of the small temple or altar of the Muses. He also indicated the remains of the theatre on the mountain slope. The French Archaeological School under P.Jamot excavated systematically in 1888, 1889 and 1890 at the site and discovered all the antiquites (G. Roux, Le Val des Muses et les Musees chez les auteurs anciens, in Bulletin de Correspondance Hellenique, 1954, 1, pp. 22-48).Wikipedia: https://en.wikipedia.org/wiki/Valley_of_the_MusesWikidata ID: Q7912361Trismegistos Geo: 2746
(Odysseus, Greek Ministry of Culture)