Gorath

From Memory Alpha, the free Star Trek reference

Gorath is a place located within Klingon territory.

There were sulfur lagoons at Gorath, and on the Day of Honor, a warrior must traverse them as part of the ritual. (VOY: "Day of Honor")

It is never revealed if Gorath is a planet or a place, but is most likely to be a place, as Moklor describes "the sulfur lagoons at Gorath".