The 'three shrines' of Ise, Kasuga and Hachiman which by the twelfth century came to be seen as a unity that protected the state. They were hierarchically positioned above a similar group of 'seven shrines' (Ise, Iwashimizu, Kamo, Kasuga, Hie, Gion, Kitano) which in turn were placed above the nijuni-sha (twenty-two shrines).
See Sanja takusen
A Popular Dictionary of Shinto. Brian Bocking.