I cannot remember anything about the story, but it was most likely from an anthology. Google has been of no help-anyway, I think it concerned a group of astronauts who land on Mars…and find an ancient abandoned city (the “City of Time”). In one of the buildings, they find a green flame…called the “Iesis flame”-which relates to another dimension…that is it. Anybody ever heard of this.
Anything ring a bell?
“The City of the Singing Flame” by Clark Ashton Smith, perhaps?