How Long could an "Eternal" Fire last?
At some point there is a fire very spiritually important to a certain people - so important that they build a city around it, and begin developing an empire with one of their main motivations being to provide fuel to the fire. They believe that if it burns strong, they will achieve success, if it falters, they will face hardships, and that if the fire ever goes out, the end of the world will soon follow.
Assuming that the fire is in a pit around half the size of an Olympic swimming pool. There's protection from the elements, disposal of ash, and expanding the pit are all easily doable. Fuels available are wood and coal (dung is blasphemous). Is it possible for this "eternal fire" to be kept burning for decades or centuries? If it can, at what point do the fuel requirements become exceedingly unreasonable (i.e. deforesting the average continent)? Are there any other obvious problems with the existence of this fire?