I have been told that visitors cannot legally go anywhere except the specified places at the specified times designated on their visa.
If Mrs. 2C had trouble getting them to take her to other site locations, it may have been because they were not specified on her visa. My understanding is that a Russian citizen can be charged with a crime if they take a foreigner to a place not listed on their visa.
Of course....your mileage may vary....depending on the type (visitor, business, etc.) visa issued. There are also limitations relative to the hosting organization.