Thousands of protesters are expected to converge on the city on the Rhine river for the two-week conference, and Bonn police told the AP they are prepared for violence.

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The leaders gathered on a footbridge over the Rhine River separating France and Germany.

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Markus Hecher is the owner of Burg Rheinstein, a castle on a scenic stretch of the Rhine River that dates back to the 13th century.

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But in one of the driest Novembers on record, Rhine River levels have dropped dramatically, revealing an unusually large trove of unexploded bombs in its bed.

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