Just had 2 great tours with Moscow city tour. I would say it is a must to have a guide for the Kremlin as there is so much to see and Moscow City Tour did us proud with their private four hour tour. We had a lovely guide NADYA who was very knowledgeable and gave us plenty of time to ourselves to take photos etc. The next day we had a private tour by car with ELENA from the same company and again had a great time finishing with coffee at the GUM store. Great guides and their website was easy to use.