In mid July we discovered this in one of the cedar trees in the front yard.
We called in a pest control service and for a mere (cough, cough, choke) $250
they happily put on their bee keeping suit,
put their can of toxic, smoky chemicals on the end of a very tall poll, knocked down the hornet nest and
provided about 45 minutes of entertainment to Xandra and Theia during naptime.
At the end of naptime, the nest was gone.