There is a mountain in Lycia called Chimaera. Methane seeps from its rock and burns without being lit, and it has done so for as long as anyone has written about the place. Ancient geographers connected the burning ground to the fire-breathing beast, and the connection is old enough that it may be the origin rather than a later gloss. It is a rare case where a monster has a fixed address.
The story around it is compact. Bellerophon is sent to kill the creature by a king who expects him to die trying, he does it from the air on Pegasus, and the usual telling has him drop a mass of lead down its throat to be melted by its own fire. The economy of that detail, using the monster's single distinguishing power to destroy it, is what keeps the episode in the repertoire.
The word has since outrun the animal. In biology a chimera is an organism whose cells come from more than one zygote, a usage that keeps the composite sense and drops the fire. In ordinary speech a chimera is something imagined and unattainable, which keeps neither. Both are live, and a reader who meets the word in a laboratory paper and in a poem on the same day is meeting two descendants of one Lycian mountain.
The mountain is still burning. It is called Yanartas now, it is a marked walk above the Lycian coast, and the flames are small enough to boil a kettle on. Very few creatures in this catalogue can be visited.