20The strong green tea served during the tea ceremony is created from highly concentrated green tea powder whisked into a froth with the bamboo utensil shown above. The whisk itself is meant to be an object of aesthetic appreciation, together with the fine ceramic tea vessels, the lacquered and embellished tea powder flasks, and the handsomely rounded kettles and pots. The chagama or tea kettles used for the tea ceremony are made of cast iron and designed to be used to heat the water used to make the tea. The lower half holds charcoal in a portable brazier, but tea ceremony chambers normally also contain a sunken hearth built into the floor that is favored in the cooler months. These heating devises sunken into the floor are also used to burn incense balls made from aromatic woods, spices and herbs. Imperial Hotel guests are welcome to savor the tea ceremony at the Toko-an upon advance reservation.