Sarnath is a city in the Dreamlands. After annihilating the ancient beings of Ib and desecrating their idol of Bokrug, the people of Sarnath flourished for a thousand years — until the night of their millennial celebration, when the city vanished without a trace.
The tale functions as a parable of hubris and divine retribution, one of Lovecraft's earliest explorations of a mythic, pre-human antiquity.