We believe the groups must be within a size that when you walk around, you cannot differentiate them from the locals or let's say they don't stand out, similar to the picture we have posted here taken during one of our Iran tours including our group tour and locals. There was a time that mass tourism was big but it is gone and what makes traveling enjoyable withing a group tour is a small group that can make the trip flexible, move around easier and make local interaction easier. It also helps us to choose hotels or services that belong to small businesses and this way we can also include small and non-touristic places in our trip itineraries.These all the reasons we don't run big groups unless it is a private request.