Located to the east of the Upper Peninsula of Michigan, Sault Ste. Marie is one of the oldest cities in the United States. Separated from its Canadian twin city by St. Marys River, it is famous among other things for its locks, known as either the Sault Locks or the Soo Locks, which enable ships to travel the metres in change in elevation between Lake Superior and the lower Great Lakes. These locks, which date back over 160 years, are considered the most important in the world due to their shipping traffic. Make sure you visit the Museum Ship Valley Camp where you can visit the interior of a former freighter that sailed on the Great Lakes for more than 50 years.