An interesting museum visit, @slowwalker.
Ando Tadao chose to exhibit these sculptures in a garden setting making use of natural elements and light.
But the setting is also artificial, as are all gardens, and in this case, the back garden is very minimalist using stone piles perhaps reminiscent of burial mounds as you remark, or possibly berms.
Berms are traditionally used to direct water flow into swales where the water is held, but in this case, the berms break up the flat topography and direct the observer to certain perspectives where sculptures can be viewed from certain angles.
It is a subliminal technique for managing perspective and certainly one I'd use if displaying sculptures outside in a garden setting.
The weather adds an unpredictable element as well ensuring that each sculpture is gradually revealed and under varying conditions.
Architecture is always about light
Have a good day, my friend.