Having a beer and some bitterballen at this country pub in the east of Holland (after a lengthy walk through some beautiful nature reserves) I noticed a plastic bag filled with water hanging from a string above every door that opened to the outside.

Most interesting : they do this to prevent mosquitos from entering inside through the open door.
Apparently the glittering of the daylight in the water keeps them mesmerised outside.

I have never seen this before anywhere in Holland, or anywhere else for that matter.