Odessa is more than 425 miles (about 700 kilometers) from Donetsk in eastern Ukraine, where pro-Russian forces have commandeered whole cities and this weekend held ad hoc referendums on independence.
It's Ukraine's biggest Black Sea port, even larger than Sevastopol in Crimea, which Russia annexed in March. Odessa lies in a region that forms Ukraine's maritime coastline and is of utmost importance to it economically.
"Ukraine without Odessa is effectively a landlocked country," said Matthew Rojansky, director of the Kennan Institute.
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Alexander Kliment, director of Russia and Emerging Market research at Eurasia Group, said unrest into those southern regions of the country would substantially weaken the Ukrainian government's legitimacy and security, though he thinks things are not yet at that point.
"If anything, the Odessa events showed that pro-Russian forces might have a significantly harder time gaining grassroots support there than they did in the eastern regions, which are closer, geographically, economically and culturally, to the Russian orbit," Kliment said.