The Laboratoire Arago in Banyuls-sur-Mer (France) was founded in 1882 by Professor Henri de Lacaze-Duthiers, one of the most famous French zoologists of the 19th century. Professor at the Sorbonne (University of Paris), he was noted for his wide knowledge of the French coastal marine fauna. In 1885, he initiated the construction of a public Aquarium, one of the first in France, which was attached to the Laboratoire Arago. This Aquarium quickly became not only a place where any eminent scientist or simple curious visitor could observe the Mediterranean diversity, but also a tool for experimentation in controlled environmental conditions made possible by the arrival of the electricity in Banyuls in 1888. Nowadays the aquarium is a tool still used as a research medium, for experiments addressing hot issues in the context of global change and the impact of pollution in the marine environment. Since 2017, by associating in the same department the Research Aquarium Centre and the Public Aquarium of the Biodiversarium, the Laboratoire Arago, now known as Observatoire Océanologique of Banyuls, offers quality facilities for scientific experimentation and an essential place for scientific mediation, where all audiences are sensitised to the preservation of the marine environment and its biodiversity.