A Keyholemandala is a construction, where you find a whole in the middle. This functions as a kitchen midden or compost, where you only throw vegetables. No fat, no meat (due to dangers for rats, only greens.
I have myself built my Keyholemandala of big stones from my garden. The keyhole is the entrance, formed like a keyhole in a door. It is easy to get the compost into the hole through the keyhole.
The first photo is from the first summer, when the Keyholemandala was quite new. The following photos are from today where I wanted to empty the compost hole. I had hoped that all compost would somehow had disappeared , but the fact is that in the bottom it had transformed to soil. There was only activity with compost worms 30 cm deep. Photo 2 shows the compost worms. Photo 3 shows how the compost looks after first layer has been removed. Photo four shows the empty hole and photo five fresh greens in the hole. Photo six is the compost on the bed. The compost is almost black compare to our soil her on Fejø