The container of this cache was a door. What shape?
The answer : round
A round door, like the one on a hobbit hole: the cache quotes Tolkien right down to its container.
The There and Back Again geocache (GC3VBMT) was hidden near Matamata, on the North Island of New Zealand, a few hundred metres from Hobbiton — the Shire set built for The Lord of the Rings and The Hobbit, and left standing ever since.
The container recreated the hobbit hole described by Tolkien: a perfectly round door, but painted a different colour from Bilbo's green and fitted with a different handle, so as to blend into the bank.
Its story is above all one of a tourist site expanding: two successive final locations were destroyed by works at Hobbiton, so much so that the first stage of the multi eventually became the final.
The answer : round
A round door, like the one on a hobbit hole: the cache quotes Tolkien right down to its container.