On the Indian subcontinent there is a species of ant with a distinct nest entrance flanked by a raised series of concentric clay rings, as though to prevent flooding. The ant seems reasonably common- at least, it is commonly photographed (see here). Locals call it a “harvester ant”. I have not seen any photographs where the ants are visible enough to identify.
The internet has two different ideas about the identity of this mystery mini-architect. One is Pheidole sykesii, which is possible, but I fear that idea may be one of those self-reinforcing internet citation circles with no verified literature behind it. The other is that this is a species of Trichomyrmex, a suggestion on twitter from several others, including at least one professional myrmecologist.
My Google-Fu has run dry, though. Do any of you know what makes these lovely mounds?