The images below show two representations of the optimal 15,112-city tour. The image on the left is a drawing of the tour upon a map of the states of Germany. The image to the right shows a solid curve representation. The tour's "inside" is drawn in blue.

The problem instance is called d15112 in the TSPLIB library of challenge examples for the traveling salesman problem.  

The tour in TSPLIB format can be found here.

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