Hidden in the most unexpected places of Extremadura (means "extremely hard or difficult), Spain there some extraordinary swimming holes like the one in the picture above. This swimming hole complete with a great rope swing is about 15 feet deep. But this post is not about the swimming hole itself but rather about the trees the hide it. Lined on both sides of the small river forming a dense green cover are a series of Common European Alder trees (Alnus glutinosa). These tree like water! So much so that if you swim in this water hole and want to get out you are required to use the tree roots that line the bank much like you would use the ladder in a swimming pool. The contour of this natural pool is part rock part tree roots.
The fruits of the Common European Alder (sometimes called "Black Alder") look like miniature pine cones measuring about 5/8 of an inch long (1.3 cm). The trees have both seed (roundish) and pollen (long and thin) "cones" although I am most likely not using the correct terminology here.
The leaves are simple and round to almost heart shaped with pronounced veins and short stems. They also have a somewhat serrated margin as can be seen in the picture below.
In the next image you can see the seed "cones" both when they are green and later when they are dried and open having released their seeds. The ones of the left illustrate the "cone" likeness.