Natural hot springs or Onsen (温泉) are numerous and highly popular across Japan. Every region of the country has its share of hot springs and resort towns, which come with them. There are many types of hot springs, distinguished by the minerals dissolved in the water. Different minerals provide different health benefits, and all hot springs are supposed to have a relaxing effect on your body and mind. Hot spring baths come in many varieties, indoors and outdoors, gender separated and mixed, developed and undeveloped. Many hot spring baths belong to a ryokan, while others are public bath houses. An overnight stay at a hot spring ryokan is a highly recommended experience to any visitor of Japan [ref]. There are many types of hot springs to enjoy. The conventional hot spring is a hot water bath. Depending on the spring, different minerals are dissolved in the water, giving it different health benefits, colors and smells. Many hot springs contain sulfur and have an according odor. Hot spring water baths come indoors, outdoors and in many different sizes. Outdoor baths are called rotemburo. While some baths are wooden or stone tubs, others are built to resemble or are actually natural hot spring pools. Some outdoor baths are spectacularly situated in the mountains, valleys or along rivers, lake or sea shores. Besides conventional hot water tubs, a popular feature of larger baths are so called waterfalls, which comfortably massage your shoulders if you sit below them. Other bath types include sand baths, where bathers are buried in naturally heated sand, mud baths and steam rooms. Ashiyu are shallow hot spring pools for bathing just your feet. They are found in the streets of many hot spring resorts and can be used free of charge [ref].