Passage 5.14.8
τὰ δὲ ἐς τὸν μέγαν βωμὸν ὀλίγῳ μέν τι ἡμῖν πρότερόν ἐστιν εἰρημένα, καλεῖται δὲ Ὀλυμπίου Διός· πρὸς αὐτῷ δέ ἐστιν Ἀγνώστων θεῶν βωμὸς καὶ μετὰ τοῦτον Καθαρσίου Διὸς καὶ Νίκης καὶ αὖθις Διὸς ἐπωνυμίαν Χθονίου. εἰσὶ δὲ καὶ θεῶν πάντων βωμοὶ καὶ Ἥρας ἐπίκλησιν Ὀλυμπίας, πεποιημένος τέφρας καὶ οὗτος· Κλυμένου δέ φασιν αὐτὸν ἀνάθημα εἶναι. μετὰ δὲ τοῦτον Ἀπόλλωνος καὶ Ἑρμοῦ βωμός ἐστιν ἐν κοινῷ, διότι Ἑρμῆν λύρας, Ἀπόλλωνα δὲ εὑρέτην εἶναι κιθάρας Ἑλλήνων ἐστὶν ἐς αὐτοὺς λόγος.
We have already given a brief account earlier of the great altar, called that of Olympian Zeus. Near it stands an altar of the Unknown gods, and after that one, altars dedicated to Zeus Katharsios ("the Purifier"), to Nike ("Victory"), and then again to Zeus under the surname Chthonius ("of the Underworld"). There are also altars to all the gods collectively, and to Hera surnamed Olympia; this one too, like the others, is made of ashes, and is said to have been dedicated by Clymenus. After it is an altar shared by Apollo and Hermes in common, because the Greeks say Hermes invented the lyre, while Apollo discovered the kithara.