Most expensive Lamborghini ever is also the least practical

Following up an insane supercar debut is easy, if you just follow this simple formula.

Start with the car that you've already got. In this case, Lamborghini's engineers started with the 700-horsepower Aventador LP700-4, leaving its 6.5-liter V-12 engine intact and untouched.

Next, grab a Sawzall and hack the top off...or have your team of industrial designers engineer an open-top variant, whichever method is easier for you.

Normally, this is the point where you'll add some sort of retractable top, call the car a "concept," and trot your new model out at the next major car show wearing a coat of your fanciest paint.

However, this is Lamborghini that we're talking about--and as we all know, the good folks at Lamborghini are a bit nuts.

The automaker decided to skip adding a cloth or hard top and just leave its new open-air Aventador J's cabin exposed to the elements.

And if that weren't mad enough, Lamborghini's designers also hacked off the windshield, necessitating a closed-faced helmet if you plan on coming close to the supercar's 217-mph top speed without a mouthful of bugs.

Okay, so perhaps I'm oversimplifying the process. Lamborghini also made other changes to make the Aventador J look and feel cohesive. For example, the interior--if you can even call it that--features body-color matched paint.

Up front, the nose benefits from new aerodynamic elements formed from carbon fiber to fit with the Aventador J's stripped-down racer aesthetic.

Large side intakes feed the V-12 engine all of the oxygen that it needs for combustion and supply valuable air flow for cooling.

You'd be forgiven for mistaking this rear wing for a fancy carbon fiber snowboard and rack.

The rear end of the Aventador J is further optimized for cooling and aerodymanics. A quad-tipped exhaust likely makes a glorious noise.

The headlamps and Y-shaped DRLs remain unchanged from the standard Aventador.

I didn't think it was possible, but the roofless Aventador J appears even more poised to pounce than the already low-slung standard model.

Here's the twist: I haven't even gotten to the craziest part. Lamborghini plans to sell has already sold this one-off example of the Aventator J for about 2.1 million euros.