Time is one of the greatest forces that has tangible effects but that we have no real control over. By demonstrating that even this brilliant city of Sarnath in all of its glory is eventually wiped out without a trace, Lovecraft is demonstrating the true nature of time, and how small our place within the universe really is.

I agree, but with a different perspective. I think what's amazing about the story is how it makes time seem so small. To mankind a thousand years is enormous, entire cultures rise and fall, existing entirely within that period. But for the creatures of Ib? A thousand years seems small, and temporary. A thousand years after their city is annihilated they still return with enough power to easily overcome Sarnath, because in Sarnath their very existence has become myth and legend. It makes us feel so small, that an entire millennia to us is just a temporary lul for Others