One of the notable ancient Greek works with science - fiction elements is 'True Histories' by Lucian. It features a journey to the moon and adventures in strange, otherworldly places.
Well, in ancient Greek, there are some texts that can be considered precursors to science fiction. For example, the myths sometimes had elements like strange creatures and other - worldly realms which are somewhat like the concepts in science fiction. Another work might be some of the philosophical musings that touched on ideas of different worlds and beings, though not in the modern sense of science - based speculation but still in a similar vein.