I can heartily recommend the Trans Siberian Railway, particularly if you just go through Russia, if you enjoy China then that is an option, I didn’t. The main problem when travelling though Russia is that they want to know everything about your trip, you need to be sponsored, very strict on visas and entry and leaving dates. I’d try and avoid Belarus, the country is a basket case with impossible beaurocracy, such that it is very hard to pre book visas except from within Europe or Russia. The train only passed through Belarus on route to Berlin, didn’t get off or stop but it still cost $300 ! From an architectural point of view I enjoyed Moscow, but the new “capitalism” is making it a very unequal society – a country that arrived just too late to get on the bandwagon.