I've been a gardener all my life so when my career took me into the construction field I became fascinated by the classic forms of garden structures and how their architecture contributes to a remarkable garden.
Moon gate is a traditional chinese entryway that leads into a contained area or frames a particular outside view. The moon gate shape announces a special area or surprise compelling the viewer to move towards the space. It's a splendid use of architecture to create a sense of mystery and privacy.
Although it's origin is china your garden need not have an asian theme. Moon gates blend well in cottage gardens as well as formal English and French versions. The shape may be used in bridges as well as arbors to evoke that air of mystery. I've even seen a circular opening in a stone wall that framed a view of the countryside beyond!