The present article deals with the inscription Perinthos-Heraklea 37, its date and importance for the history of the provincial capital of Thrace Perinthos. Based on the appellations used for Hadrian it is suggested that it is connected with the imperial decision to include Perinthos and its elite into the founding members of the Panhellenion league, which was established in Athens in AD 131/132. It seems that on his way to Athens Hadrian visited Thrace and Perinthos in the autumn of 131 when he took the decision. If so, the inscription should be dated between AD 131–138. The nature of the building lavishly decorated with imperial statues and icons remains unclear, but may belong to a type of sanctuary filled with imperial statues as the Olympieion in Athens and perhaps in the neighbouring Maroneia.