Moscow to be honest was a bit of a disappointment, it is no where near as nice as St Petersburg and the people are a lot less friendly. It is not really set up that well for tourists, although I suppose it has only been open to foreigners for about 15 years.
I'm definitely glad I went as it is pretty symbolic to be stood in the middle of Red Square or to walk around the Kremlin. Also seeing Lenin's mausoleum was cool although a bit weird and morbid, seeing he has been dead since 1924!
The Moscow underground is also an experience not to be missed as it takes quite a while to work out it all out.
My Trans-Siberian rail journey also started in Moscow which was quite cool, the train itself was really nice , and I was sharing a 4 berth carriage
with only one Russian lady which was cool and seeing her English was only just marginally better than my Russian it was an interesting 24 hours.