An international company of some repute, Gassan’s jewelry stores have spread into airports across the world, but their HQ is still based in the remarkable Amsterdam School building designed by J.N. Meyer in 1897, overlooking the Oudeschans canal. It is here that the founder of Gassan first learned to cut diamonds; free, guided tours of the factory are available daily and incorporate a visit to the onsite Choices by DL Flagship boutique, where whopping great precious stones are sold at whopping great prices. There are three other stores in Amsterdam, one at Rokin 1–5 in the Old Center, plus two more out at Schiphol airport. Considering the company’s size and standing, it is one of the better options to head for if you are thinking of investing in gemstones.