Typically if you hold a demonstration in any place where commerce exists the police will curtail, move, as in cordon off, or shut down the event. From the standpoint of a demonstration or protest this is not very efficient. Mostly it just gets the event on the local news and folks think the demonstrators look like amateurs.

Tours may be more efficient. Very popular and slow walking tours. Tours including 100K or so pedestrians could certainly serve to clog up, say, a section of a city. And the police would be working the detail instead of interfering.

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