Adjacent to the Arboretum of the 40th Parallel North, on the highest level of the terraces, lies a particularly distinctive collection comprising more than one hundred endemic Mediterranean, Iberian and Ibero–North African species. These plants are of great botanical and educational value, but above all stand out for their unquestionable taxonomic and ecological uniqueness. Due to the vulnerability of their populations—resulting from their rarity and generally very restricted distribution—they require comprehensive conservation programmes.

Iberian endemics. Species exclusive to the Iberian Peninsula, such as Artemisia assoana, Berberis vulgaris subsp. seroi, Delphinium fissum subsp. sordidum / D. bolosii, Digitalis obscura, Echinospartum boissieri, Genista pumila subsp. rigidissima, Genista umbellata, Helianthemum asperum, Iberis saxatilis, Linum appressum, Nepeta nepetella subsp. aragonensis, Phlomis crinita, Ptilostemon hispanicus, Salvia candelabrum, Salvia lavandulifolia, Teucrium homotrichum, Thymus bracteatus, Thymus zygis, Vella pseudocytisus subsp. paui and subsp. pseudocytisus, Vella spinosa, and many others.

Ibero–North African endemics. Plants whose global distribution is shared between the Iberian Peninsula and North Africa, such as Bupleurum fruticescens, Cytisus fontanesii, Echium boissieri, Juniperus oxycedrus subsp. badia, Pyrus bourgaeana, Retama sphaerocarpa and Stipa gigantea.

Mediterranean endemics. Species unique to the Mediterranean basin, including Aphyllanthes monspeliensis, Asparagus acutifolius, Bupleurum fruticosum, Cistus creticus, Crataegus laciniata, Erinacea anthyllis, Genista cinerea, G. scorpius, Hyssopus officinalis, Jasminum fruticans, Juniperus oxycedrus subsp. oxycedrus, Olea europaea, Phillyrea latifolia, Pistacia terebinthus, Plantago sempervirens, Quercus coccifera, Rhamnus alaternus and Smilax aspera, among others.