Altar? Who knows what this is?

22 Jan 2018 | Archive 2018

Near the ’duckpond’, close to a tree in the grass of the flowery meadow, somebody has been erecting a sort of altar, lately. It also looks as if something has been buried. There have been placed stones, plants, but also rotten food such as fishes-heads.
Do you know what this is, or who has done this? Is will be removed, but a warning it advance might be in order.