The lower basin of the Jarama River is the river axis that links the main elements of the Regional Park of the Southeast. The rich alluvial plains hide 132 artificial lagoons that are authentic distributors of exclusivity and biological diversity. The origin of these valuable wetlands is the extraction of aggregates in the open air, digging enormous holes until breaking the water table and causing the flooding of the gravel pit with water from the river basin. In a short time, the banks of these particular artificial ponds are covered with rushes, reeds, cattails, tamarisks, willows, ash trees and elms, developing leafy belts of marsh vegetation that constitute a magnificent habitat for different groups of aquatic birds, reptiles and amphibians. The gypsum cliffs are also an indispensable environmental element to delve deeper into the surprising natural wealth of the regional park and enrich the aesthetic quality of the landscape. The striking grey and whitish cliffs, with a fragile and arid appearance, are formed by large layers of marl and gypsum sediments piled up during the Miocene while large masses of water containing abundant mineral salts were evaporating. The steep and desolate appearance of these unique reliefs, together with the toxic nature of a substrate rich in calcium sulphate, conditions the development of the plant species that colonize the unstable cliffs, unique and sometimes endemic plants adapted to the demanding conditions in this exclusive geographical section of the park.