In Greece, if you own a pool of over 25 meters squared under the tax law you are required to add an amount to your assessable income of sometimes close to 20,000 euros.
The policy is designed to be both a luxury tax and an acknowledgement that you must have paid for the pool from income you probably did not declare (I love the way there is an assumption that everyone who is rich has not declared all their income).
But in Greece you can buy floating tiles, so that when you are not using the pool you can walk over the pool and no one will ever know there is a pool.
This product did not exist until it was announced that the revenue authority in Greece had used google maps to find that, rather than the 300 pool that had been declared in Athens suburbs, there were well over 16,000 that were large enough for this tax to apply.
Since then there has been an amazing increase in their sales.
I wonder what public finances would look like in Greece if the Greeks took their world leading passion for avoiding taxes and applied that passion to anything even slightly productive?