Grenen

Grenen marks the junction between the strait of Skagerrak (part of the North Sea) and the Kattegat sea, and the turbulent colliding seas have created a 4-km long curved sandbar above and below the waves stretching east. The reef is still active and has grown about 1 km northeast towards Sweden over the last century, resulting in a mean annual growth rate of about 10 m.

Råbjerg Mile

Råbjerg Mile is a migrating coastal dune between Skagen and Frederikshavn, Denmark. It is the largest moving dune in Northern Europe with an area of around 2 km2 (0.4 mi2) and a height of 40 m (130 ft) above sea level. It is also the only major stretch of migrating dunes in Denmark. The dune contains a total of 4 million m3 of sand. The wind moves it in a north-easterly direction up to 18 metres (59 ft) a year. The dune leaves a low, moist layer of sand behind it, trailing back westwards towards Skagerrak, where the Mile originally formed more than 300 years ago. Over 250,000 people visit the dune every year.