'Every High Hill' in the Bible

"For from long ago you have broken your yoke, you tore to pieces your bonds. And you said, 'I will not serve!' But on every high hill and under every leafy tree you [were] lying down [as] a prostitute.

Then Yahweh said to me in the days of Josiah, the king, "Have you seen what apostate Israel has done? She has gone on every high hill and under every leafy tree and she has prostituted [herself] there.