Grenen: The Northernmost Tip of Denmark Grenen is the iconic, sandy peninsula located at the absolute northernmost tip of Denmark, just a few kilometers north of the historic town of Skagen. It is one of the country's most spectacular and visited natural wonders. Where Two Seas Meet The most famous feature of Grenen is the unique maritime phenomenon that occurs at its very tip: the collision of two distinct seas. Here, the Kattegat (flowing from the Baltic Sea) and the Skagerrak (flowing from the North Sea) meet head-on. Because the two seas have different currents, densities, and salinities, their waves clash directly against each other in a visible, turbulent line. Important Note: Due to these incredibly strong, colliding currents and unpredictable undertows, swimming at Grenen is strictly forbidden—though visitors love to stand in the shallow water with one foot in each sea.