We have a species of wasp or hornet which nests in or around our house/garage from about May until October. They look identical to a 'standard' wasp, but are at least twice as big – most of them are easily 1.5 inches long – rather frightening when you see one flying in your direction.
Normally they are not aggressive, but will respond to electric lights, so become a risk at night – open a door or window to a room with a light on, and two or three will turn up virtually instantly. The good thing is that they make one hell of a buzz, probably due to their size, so its not difficult to tell they are around.
Very difficult to get rid of – for ecological reason I prefer not to kill them, but once they are in the room, killing is about the only way to do it. The local bug spray is crap. I won't give the name, but it is obtainable in most of Europe. It says on the tin 'instant action' – maybe, if you hit them with the tin, 'cause the spray don't affect them (or flies, mosquitoes or any other flying insect that I can see). So now we are trying to learn to live with them.
They do build beautiful nests, about the size of a rugby ball, and its a real architectural masterpiece, which they abandon each year. Although they will return to nest in the same location, they always build a new nest.