Trekking can be done anywhere in the world. Several areas are particularly popular with travelers, including the mountainous regions such as the Himilayas in Asia and the Andes in South America. However, treks have been organized in other less-touristed areas regions on almost every continent. Trekking can result in a trip as long or short as participants decide, from trips of a week or more to expeditions that last more than a year. Trekking can be as athletic and adventurous as participants decide. The less-structured nature of trekking and a world of destinations help attract a wide variety of participants to the activity. Several pieces of gear help make trekking more enjoyable. One is a comfortably-fitting backpack. Many trekkers travel for extended periods and need to carry all of their belongings with them. A sturdy backpack can comfortably fit more than 20-40 pounds (10-20 kilos) of clothing and gear. Another important item is sturdy hiking boots. When covering long distances, wearing the right pair of boots can make the difference between enjoying a trip and being in pain. Other survival equipment, such as warm clothing, a first aid kit and a supply of food and water are also very important. Trekking is best attempted initially with someone who has experience or in a professionally-led group. This can help introduce those new to trekking to the special skills required to successfully make an overland journey of significant length. A number of outdoor stores and organizations offer classes and plan trips that can help give an idea of the gear and physical ability required in trekking.