Should you be at the Rouge-Cloître, walking along the Chemin des Étangs on the northern bank of the Grand étang de Clabots, perhaps on your way to pay your respects to René Stevens, you could be forgiven for not noticing this square-shaped stone.
This is, I believe, a stone boundary post which possibly marked the limit of the Priory’s lands. There is another alongside the Lindevijver at Groenendaal. In the Bosmuseum there (free to enter, free toilets too), you can find an unearthed specimen, fully one metre tall.
What you see in the ground, like an iceberg at sea, is merely the tip.