2 Kings 17:9

And the children of Israel wrapped themselves in things that were not well toward the LORD their God. And they built them Hill altars in all their cities, both in the towers where they kept watch and also in the strong towns.

2 Kings 18:8

He beat the Philistines even unto Gaza and the coasts thereof, both in castles of garrisons and strong cities too.

Deuteronomy 13:6

If thy brother, the son of thy mother, or thine own son or thy daughter or the wife that lieth in thy bosom or thy friend which is as thine own soul unto thee, entice thee secretly, saying, 'Let us go and serve strange gods which thou hast not known nor yet thy fathers,

Deuteronomy 27:15

Cursed be he that maketh any carved image or image of metal - an abomination unto the LORD, the work of the hands of the craftsman - and putteth it in a secret place.' And all the people shall answer and say, 'Amen.'

Job 31:27

Hath my heart meddled privily with any deceit? Or, did I ever kiss mine own hand?

Ezekiel 8:12

Then said he unto me, "Thou son of man, hast thou seen what the Senators of the house of Israel do secretly, everyone in his chamber? For they say, 'Tush, the LORD seeth us not, the LORD regardeth not the world.'"

Hosea 12:11

But at Gilead is the abomination, they are fallen to vanity. At Gilgal they have slain oxen: and as many heaps of stones as they had in their land furrows, so many altars have they made.

Treasury of Scripture Knowledge

Summary

And the children of Israel did secretly those things that were not right against the LORD their God, and they built them high places in all their cities, from the tower of the watchmen to the fenced city.

From the tower

Bible References

Secretly

Deuteronomy 13:6
If thy brother, the son of thy mother, or thine own son or thy daughter or the wife that lieth in thy bosom or thy friend which is as thine own soul unto thee, entice thee secretly, saying, 'Let us go and serve strange gods which thou hast not known nor yet thy fathers,
Deuteronomy 27:15
Cursed be he that maketh any carved image or image of metal - an abomination unto the LORD, the work of the hands of the craftsman - and putteth it in a secret place.' And all the people shall answer and say, 'Amen.'
Job 31:27
Hath my heart meddled privily with any deceit? Or, did I ever kiss mine own hand?
Ezekiel 8:12
Then said he unto me, "Thou son of man, hast thou seen what the Senators of the house of Israel do secretly, everyone in his chamber? For they say, 'Tush, the LORD seeth us not, the LORD regardeth not the world.'"

From the tower

2 Kings 18:8
He beat the Philistines even unto Gaza and the coasts thereof, both in castles of garrisons and strong cities too.
Hosea 12:11
But at Gilead is the abomination, they are fallen to vanity. At Gilgal they have slain oxen: and as many heaps of stones as they had in their land furrows, so many altars have they made.