A church in Japan's Seto Inland Sea has been designed by local design studio Hiroshi Nakamura&NAP. The church is halfway up the hill with panoramic views of the sea. The church is mainly used for weddings and is located in the garden of a resort hotel in Onomichi, Hiroshima. By winding two spiral staircases, a self-contained structure is achieved that embodies the act of marriage in its pure form architecturally. It is essentially a building of pure flow.

A single spiral stairway would be unsteady in a horizontal direction and is prone to vibration in a vertical direction, hence, very unstable.By joining two spiral stairways so that one supports the other, produced a free-standing structure. Just as two lives go through twists and turns before uniting as one, the two spirals seamlessly connect at their 15.4m summit to form a single ribbon. The chapel aisle looks toward an existing symbol tree. The altar stands before the tree, and 80 seats are positioned for views to the ocean through the trees.

Ordinarily, a building is composed of distinct elements: roof, wall, and floor. Here, however, the entwining stairways perform as roofs, eaves, walls, and floors to produce the building’s spaces. The stairways widen in breadth in response to location and function, such as at the summit where the couple meets, in directions having fine views, and in places where the eaves must be deep to shield the interior from the sun.

The building’s exterior is finished in upright wood panels, painted white so as to deepen in beauty as time passes, and titanium zinc alloy, a material resistant to damage from the sea breeze and pliable enough to be applied to curvature. Employing the zinc alloy on the coping, walls, ceiling, and window sashes enabled a simple design unified by means of a single material.