Resumen: The book describes the characteristics of the species Cordulegaster boltonii (Donovan, 1807) (Odonata, Cordulegastridae) in the Central System of the Iberian Peninsula, a mountain range about 500 km long. It specifically addresses aspects related with its habitats (rivers and mountain streams), its morphology in the larvae instar and the imago or flying adult, as well as its behaviour. The book presents some of the data obtain through a literature review, being the majority of the data original and obtained through the study of that population on the referred area. A special attention was given to the larvae and exuviae, across the whole period of emergency. Among the data collected, we outline: a) the phases of larvae development, F-3 to F-0, can be distinguished through the analysis of the measurements of the heat width and wing sheaths; b) the presence of stream slopes seem to influence the amount of larvae stage F-0: the larger the stream slope, the bigger the proportion of these larvae; c) the majority of the larvae emerge less than 5 m from the rim of the streams (in almost 97% of the cases); d) the presence of direct sunlight influences the area where the larvae emerge: 90,5% emerge in areas exposed to the sun; e) sex ratio is statistically balance during the emergency period, with no predominance of male or female. On the mountains, where the study was conducted, Cordulegaster boltonii is present in a wide variety of streams and altitudes.