These structures - Termitaria - are constructed by the fungus-grower termites Macrotermes mossambicus. Fungus gardens are situated near the base of the termitary.
Termites are often erroneously referred to as 'white ants' - termites are not true ants.
A pic to show just how huge these mounds can be - they do get taller than this.
A termitary built around the base of a tree, it doesn't seem to affect the tree at all.
The mounds are most distinctive in the rising or setting sun - this pic was taken on a cloudy day.
They come in all shapes and sizes, the color being dependent on the soil they're built on.
The hole in this one was probably made by an Antbear or 'Aardvark' hunting for food - I wonder who lives there now?
In his book The Soul Of The White Ant, Eugene Marais puts forward the theory that a termitary is a separate composite animal.
This one has been worn smooth - it's been used by Elephant and/or Rhino as a scratching post.
Here's a link to an earlier post I did on the yummy giant mushroom found on these termitarium during summer: Omahova
Amy Schoeman - Notes On Nature.