Rolls-Royce worked with Dutch fashion designer Iris van Herpen to make its most elaborate one-off vehicle yet.

Unveiled Monday, the Rolls-Royce Phantom Syntopia is the "most technically complex commission ever undertaken" by the automaker's bespoke division, according to a Rolls press release. The one-off sedan took four years to develop and build for the unnamed client that commissioned it.

Based on the extended-wheelbase version of Rolls' flagship sedan, the Phantom Syntopia features an iridescent paint job that appears solid black at first, but shows purple, blue, magenta, and gold undertones in sunlight. A wave design on the hood also appears when viewed at certain angles. To achieve these effects, Rolls used a new technique that involved adding pigment to the clear coat, a process that took several months and involved over 3,000 hours of testing and validation, according to the automaker.

The interior's built-in picnic tables got their own elaborate paint job with the same wave design. Rolls used black paint mixed with 0.9% glass particles, then added clear coat with 1.4% of the shimmer mixture used for the exterior, a process that took over three weeks to complete.

The wave design is repeated on the interior's illuminated Starlight Headliner with 995 fiber-optic elements. The light-up headliner is a signature Rolls feature, but the automaker claims this is the most complicated version yet. The Syntopia headliner was made from a single piece of leather chosen from over 1,000 hides. It's layered on woven nylon fabric that shows through in spots, intended to create a spine-like, three-dimensional look, and garnished with 162 petals made from glass organza, a shiny fabric used in haute couture.

The wave and petal themes were repeated for the artwork in the "Gallery" display window housed in the Phantom's dashboard. All told, assembling the headliner took 700 hours of work by the Rolls and van Herpen staffs, while the Gallery art took 60 hours to complete.

For the upholstery, Rolls went with a throwback theme. Many early luxury cars had open driver's compartments, which were trimmed in leather to withstand the elements, and enclosed passenger compartments with fabric upholstery. While still fully enclosed, the Syntopia has leather front seats, while the rear seats are upholstered in quilted, silk-blend fabric that has a shimmering appearance similar to the headliner.

The Syntopia is also the first Rolls to get its own scent. According to Rolls, it's based on cedar wood from the client's home region, with hints of iris, leather, rose, and lemon mixed in. It gets spritzed from patented dispensers in the headrests, which took more than two years to develop, according to Rolls. That included testing in extreme heat and cold to ensure the scent "maintains its distinctive profile in all conditions," the automaker said.

The Rolls-Royce Phantom Syntopia is scheduled to be delivered to its owner in May. Rolls claims it won't be replicated, but the automaker's return to coachbuilding and continued emphasis on bespoke work means we'll likely see more extravagant builds like this, as well as limited editions like the three-off Boat Tail.