A Speakers' Corner is an area where open-air public speaking, debate and discussion are allowed. The original and most noted is in the north-east corner of Hyde Park in London.
Historically there were a number of other areas designated as Speakers' Corners in other parks in London (e.g., Lincoln's Inn Fields, Finsbury Park, Clapham Common, Kennington Park, and Victoria Park).
More information on the Wikipedia page [1]