Since there are already geographically segmented Travel forums, why not just put all restaurant reviews and forum questions in "sister sections" to those forums? The system now goes, for example:

--Travel&Dining
----Featured Destinations
-------London
-------New York


So my suggestion would be:

--Travel&Dining
----Featured Destinations
-------London
---------London travel
---------London dining
-------New York
---------New York travel
---------New York dining

and so on.