Revelation 12:3
And there appeared another wonder in heaven; and behold a great red dragon, having seven heads and ten horns, and seven crowns on his heads.
Nave's Topical Index—AKJV

Revelation 13:1
And I stood on the sand of the sea, and saw a beast rise up out of the sea, having seven heads and ten horns, and on his horns ten crowns, and on his heads the name of blasphemy.
Nave's Topical Index—AKJV

Revelation 17:9
And here is the mind which has wisdom. The seven heads are seven mountains, on which the woman sits.
Nave's Topical Index—AKJV