Bobity.

Many years back I done a series of posts on a GEOTD theory. I have since learnt to limit the word count on posts. TL-DR The natural habitat for Dragons are volcanoes. Therefore... Dragonriding cultures throughout history lived near volcanoes. Therefore... Evidence of Age of Heroes dragonriding cultures could be found at volcanoes (gargoyle architecture). Therefore... Dragonstone Castle dates back to the Age of Heroes. AND The super massive volcano Marahai in the Jade Sea, which shows evidence of a recent massive eruption in the form of a caldera larger than anything on earth was likely the home of the GEOTD, before it blew up and all physical evidence of the GEOTD kicking off a volcanic winter, AKA the Long Night

Throughout ASOIAF depictions of sphinxes had always been as 'Valyrian' with dragon bodies and human heads, except for one reference. AFFC - Samwell V - 'The gates of the Citadel were flanked by a pair of towering green sphinxes with the bodies of lions, the wings of eagles, and the tails of serpents. One had a man's face, one a woman's.' While not a riddle per say, the discrepancy of the anatomy of a sphinx is puzzling, especially if the Citadel predates Valyria with references during the Age of Heroes.

Do folks outright disregard Age of Hero references to dragons? I think the Valyrians were experimenting on creatures to replicate dragons, but dragons were already around. I don't buy the "We were mere sheppards" line.