There were once dwarf sauropods living on the islands that are now the Carpathian Mountains. These dinosaurs were not much bigger than a horse, and lived along side miniature ankylosaurs and tiny iguanadonts. Which makes me think of a Lost World-type setting, deep in the untamed wilderness in the heights of Romania. There, the dinosaurs have survived, along with the bears, wolves, lynxes, and vampires.
This is a setting mash-up, taking two common tropes and stirring them together to see what happens, triggered by the geographic overlap of their real-world sources.
There are two ways to do this.
Vlad III, Exiled Prince of Lost Wallachia
It’s the mid-15th century, the height of the Ottoman Empire. A young Wallachian nobel by the name of Vlad has been overthrown and exiled, so now he is leading a guerrilla war against the Ottoman puppet on the throne, using his unstoppable sauropod cavalry, packs of clever hunting velociraptors, and vicious flying microraptors.
So you have the Ottomans in an even more alien environment, a dense jungle, high in the mountains, cut off from the rest of the world, where the plants and animals are completely unexpected. And where the natives are familiar with them, and taking advantage of their unique capabilities. Magyarosaurus is more powerful than a horse, yet can much more easily navigate the dense jungles, and where hawks are stymied, microraptors are at home.
It’s the late 19th century, and as the European empires push ever further into the jungles of Africa and Southeast Asia, there remains an unexplored part of Europe: high in the Carpathian mountains hides a lost world where the dinosaurs still walk and vampires are real. During the day, explorers can marvel at the fantastic beasts, but at night they had better make their camp securely, or not all of them will wake up. The primitive people that live here alternately worship and appease the vampire lords that control all of what passes for civilization.
This is just a fragment, a little snippet that popped to mind. I’m tossing it out there, in the hopes that someone will find something amazing to do with it.