The National Mall is the great promenade that connects the most important building of the capital of the United States: the capitol with the George Washington and Abraham Lincoln Memorials touring the Castle and the main Smithsonian museums and the National Gallery of Art. The fountains present inside and outside these museums suffer alterations of color and texture due to colonization of algal populations on the surface of ther constituent materials. We have studied 9 fountains belonging to the National Gallery of Art, the Smithsonian National Museum of African American History and Culture, the Smithsonian Museum of Contemporary Art (Hirshhorn), the Smithsonian Arts and Industries Building,m the Smithsonian Institution Building (the Castle)m, the Smithsonian National Museum of American History and the Smithsonian Natiobnal Museum of the American Indian. In this work carried out by the national Project VIRARTE (UGR-MEC) at the Smithsonian Museum Conservation Institute (MCI-SI), the relationship betweeb the diversity of the algal groups and the material composition and typology of the fountains is studied. We have studied the presence of different species of green microalgae, blue-green microalgae and diatoms that form pustules, films, mats and minteral crusts on fountains constructed with granite, limestone and various metals, and even upon sealant resins that are used to repair water leaks. The ultimate goal of this work in the control of these formations to avoid the aesthetic, functional and material damage that these photosynthetic organisms produce in the architectural heritage associated with water.