Russia. I've traveled to 11 of the 15 former Soviet Republics but this is my first visit to Mother Russia. I know better than to assume what I'll find.
Vladivostok, "the San Francisco of Russia", is the Eastern terminus of the Trans-Siberian.
The omnipresent hills fit the comparison and the seafood is excellent at a fraction of SF's prices. The service is very friendly as well. I hadn't expected the level of service from my experience at getting the Russian visa.(Whatever you do, don't smile.) The State Art Gallery has some very nice Russian pieces but all in all I wouldn't return to Vladivostok but for the food.
Before even beginning the train journey, take a look at a map of Russia. Draw an anemic line across from East to West, from Vladivostok to Moscow. and realize that I will see almost nothing of this vast country. Russia is almost twice the area of the U.S., including Hawaii & Alaska.
New York to San Francisco is 2903.3 miles via I-80. Vladivostok to Moscow is is 9,140.7 kilometers (5700 miles) and it's another 781.7 miles via the M-9 to Kaliningrad, our westernmost destination. That's 11 time zones.
Compared to Russia, "the U.S. is basically an overcompensating, attention-seeking brat."
My travel buddy and I will be on the train for 7 full days.