NEW YORK, United States — Hidden above the main jewellery floor at Tiffany & Co.'s flagship Fifth Avenue store, beyond the gleaming glass cases of gold engagement rings and sterling silver bracelets, there is a secret salon few shoppers know exists — or will ever get to see.This exclusive venue is for Tiffany’s high-end clients, those looking for rare gems, massive diamonds or bespoke creations that can cost millions of dollars. They can dine, drink and luxuriate for the day as they peruse its stunning selections. For Melvyn Kirtley, the retailer’s chief gemologist, this is where Tiffany gets to show off its most prized jewellery.“We built this lovely area, which was really to resemble a wonderful New York City apartment,” says Kirtley, who has worked at Tiffany for 35 years. “Here we can show our customers in a very private way wonderful jewellery. We can work with them on incredible custom designs. This environment really does lend itself to that type of experience.”A current highlight at the secret salon is Tiffany’s otherworldly Paper Flowers collection, the first jewellery designs from creative chief Reed Krakoff, who joined the gem house last year. In one case sit shimmering platinum pieces outfitted with diamonds and blue tanzanites, all made to look like little floral fragments. Prices range from $2,500 to $790,000.We can show our customers in a very private way wonderful jewellery. We can work with them on incredible custom designs. This environment really does lend itself to that type of experience.Many of these sparkling delights are made right in the store. High atop the sales floor and secret salon, Tiffany’s most elite craftspeople sit at desks full of polishing wheels, drill bits and torches where they sculpt “high jewellery,” platinum diamond leaf earrings, melo pearl necklaces and golden bird brooches. Astonishing items are created here, such as a 26-carat yellow diamond ring and a bib necklace rippling with 3,000 stones.Though surrounded by luxury redoubts such as Bergdorf Goodman, Gucci and Louis Vuitton, its imposing headquarters looms large. It is, after all, the most famous jewellery store in the world, a 181-year-old company that once brought the French crown jewels across the Atlantic. As a brand, it exists in a dreamy wonder-world of conspicuous consumption, thanks in part to Audrey Hepburn in the 1961 film "Breakfast at Tiffany's."Chief executive officer Alessandro Bogliolo said he considers the store a “precious property.”Bogliolo was brought on to reinvigorate Tiffany for the 21st century. Buzzy new marketing is attracting shoppers, sales have rebounded with refreshed jewelry lines, stores have been reimagined and logistics improved. The flagship store is key to that revitalization, he says, since it can account for as much as 10 percent of worldwide net sales.As a result, Tiffany is planning a full renovation of the building, with construction set to begin in spring 2019. The retailer will spend as much as 2 percent of its worldwide net sales on the project over the next three years, which means it’ll cost up to $250 million, according to Bloomberg calculations based on last year’s revenue.Less than half of the building is devoted to sales space. Bogliolo plans to change that by replacing office areas with retail floors — including a lot more room in the secret salon for VIPs mulling their next purchase of a $4 million diamond ring.By Kim Bhasin; editor: David Rovella.