Passage 9.8.3
ἐκ δὲ τῶν Ποτνιῶν ἰοῦσιν ἐς Θήβας ἔστιν ἐν δεξιᾷ περίβολος τῆς ὁδοῦ τε οὐ μέγας καὶ κίονες ἐν αὐτῷ· διαστῆναι δὲ Ἀμφιαράῳ τὴν γῆν ταύτῃ νομίζουσιν, ἐπιλέγοντες καὶ τάδε ἔτι, μήτε ὄρνιθας ἐπὶ τῶν κιόνων καθέζεσθαι τούτων μήτε πόαν τὴν ἐνταῦθα μήτε ἥμερον ζῷον μήτε τῶν ἀγρίων νέμεσθαι.
As you travel from Potniae toward Thebes, there is on the right side of the road an enclosure that is not large, containing pillars within it. There, they say, the earth opened to receive Amphiaraüs, adding further this tradition, that no birds perch upon these columns, nor does any grass grow there, nor do animals, either domestic or wild, graze upon the spot.