The Balkans
The Balkans, which consist of Albania, Bosnia and Herzegovina, Bulgaria, Croatia, Kosovo, Montenegro, North Macedonia, Romania, Serbia, and Slovenia, are generally thought of as a target for Russia, even if it would be hard to get to them without having to trample over other countries. Not to mention that some are NATO members, like Romania and Bulgaria (which are also considered part of the Balkan countries).
Despite this, the way in which Russia could try to gain control over the region would be to destabilize it, with the help of Serbia as it has always been pro-Russian. Why would Putin want to gain control of this region? It is because, even if none of the countries in the Balkan peninsula haven’t been under the Kremlin’s rule, Russia always considered them under their sphere of influence. Especially since they have always backed Serbia, the biggest state in the West Balkans after they had started a civil war in the region in the 1990s.
The repercussions of that war are still seen today, with many separatist and nationalist extremists in the region, as well as countries that are not recognized by Serbia or Russia. EU peacekeepers have always been present in Bosnia and Kosovo, especially since some of the countries have expressed their intention of joining NATO or the EU.
With the Russian embassy in Kosovo warning against Kosovo’s intention of joining NATO which will force them to “react to this hostile act.”, and Serbia also being hostile against this decision, the region is not safe were Russia, their Serbian allies, or other extremists to take advantage of the chaos in Ukraine to strike as well.
If you are curious about why the war broke out between Russia and Ukraine, you can read more about their complicated history here!