According to the legend, dannebrog fell from the sky near Lyndanisse, during the final battle between the Danes and the heathen Estonians in the year 1219.
It consists of a white cross with red squares to fill out the holes in the rectangle.

The exact proportions are: Length:Height 4:3
Length: 3-red, 1-white, 4½-red (+3/4 red for wear and tear).
Height: 3-red, 1-white, 3-red.