Tatami

Tatami are the woven rush-grass mats that cover floors in Japanese rooms, about 6 feet by 3 feet, soft underfoot, with that unmistakable grassy smell when they're new. You'll meet them in any decent ryokan (Hoshinoya, Tawaraya in Kyoto, Aman Kyoto), and in the Japanese-style suites at urban Park Hyatts and Four Seasons. Rules of the room follow the tatami: shoes off, no walking on the borders, futons get unrolled directly on top at night. Sizes of rooms are still measured in mats ("an 8-mat room"). The mats need replacing every few years, which is why a freshly tatami'd ryokan smells the way it does.