I went on the city centre tour first and we had Simone (sp?) and he was fantastic, he is training to be a teacher and these tours are a way of testing his knowledge and what he can remember. I really enjoyed it so I decided to go on the colosseum tour as well, the guy doing that wasn't as talkative, but he knew some spots to see fantastic views of the forum and told us to get our tickets from the forum instead of the colosseum to avoid queueing (an invaluable tip!). The tours all start at the Spanish Steps and both tour guides told us different things about the place that the other tour guide hadn't which I like because it wasn't just one basic script they read from.
Only thing I would say is that it's not as obvious to find as it sounds on the website because MacDonalds isn't allowed all it's signs as Rome is a historic city and it would spoil it, it's to the right of the steps as you are looking at them, just keep walking until you come to it. It is run by MacDonalds though so I doubt they'll change that.
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