en_tn/2ki/16/04.md

the high places, on the hilltops, and under every green tree

These are places where the people of the other nations worshiped their false gods.

under every green tree

God wanted his people to offer sacrifices to him in Jerusalem. The word "every" here is an exaggeration to show how determined King Ahaz was to disobey God by offering sacrifices in many other places instead. Alternate translation: "under many green trees" or "under many green trees around the country" (See: rc://en/ta/man/jit/figs-hyperbole)