I booked this tour online on a whim, as we had a 5 hour wait between flights and I thought we could see the City in that time.
Yep we did, and it was great!
Our guide was impressive in not only her knowledge and attention to the detail of the city but in her caring attitude and her ability to swap from English to Spanish and make sure she treated each group with a fairness of time and attention.
She took photos of us for us and she made sure everyone was present when she got us all round the pretty Old City.
The cog train ride was great and the usual passengers didn't seem to mind that our group took over the train and never stopped clicking and pushing to get the best place to get the next picture.
The only problem was nothing to do with the tour and its content. It was the fact there was not enough signage from the railway station to get to the bus station, and no one seemed to know or care - if they spoke English that is. So get a map from the the airport to the train tracks and then from the station to the bus station, and use the station toilet, as the one at the bus station is one of those automated ones that was not pleasant!
We loved the tour and as we have so many Swiss Francs left we're going to have to find another trip to go on in Switzerland and we'll certainly use Viator again!