The Grotto of Animals:

a Sixteenth-Century Hydraulic Device

The Grotto of Animals is one of the most significant architectural features in the gardens of the Medici Villa of Castello, and is one of the earliest examples of the Italian formal garden. Set within a context celebrating the Medici dynasty, the grotto is considered the prototype for the artificial grottos that spread across Italy and Europe from the mid-sixteenth century onwards. It was designed by Niccolò Pericoli, also known as Il Tribolo, alongside the garden. Since 2013, the villa has been listed as a UNESCO World Heritage Site.

Carved through a complex excavation process and enclosed by a substantial retaining wall, the grotto was designed to resemble a natural cavern: dark and damp with calcareous deposits and shells, and featuring waterfalls concealed within the sponge-lined ceiling and mosaic floor. Three niches house marble basins surmounted by zoomorphic sculptures, including a lion, a giraffe, a rhinoceros and a unicorn, which were designed to inspire wonder. Originally, the space was also adorned with bronze birds by Ammannati and Giambologna, which are now housed at the Bargello Museum.

The grotto's defining feature is its sophisticated hydraulic system, which is still extant today and powered the water displays. A network of channels distributed across several levels conveys water from the Vasca del Gennaio into the grotto, along the retaining wall and towards the ninfei. Another stone and terracotta duct, positioned above the vaulted ceiling, branches into lead pipes to create the dramatic 'Diluvio' (flood) effect. A further channel beneath the floor collects runoff water and redirects it towards the Giardino degli Agrumi. These narrow, complex passageways are inaccessible to the public and can only be entered by technical staff.

Until recently, documenting these spaces, particularly those within Mannerist gardens, posed significant challenges. Their organic forms made it difficult to use traditional surveying techniques, often resulting in overly simplified and unsatisfactory representations. This was an even greater challenge when it came to the hydraulic tunnels, which were narrow, unlit and difficult to access, with minimal openings and complex spatial layouts.

However, the advent of high-resolution 3D surveying technologies, such as laser scanning, has made it possible to overcome these obstacles. Since 2012, the Geomatics Laboratory at the University of Florence, in collaboration with the Regional Directorate of Museums of Tuscany, has been working on a documentation project covering the entire complex, including the grotto, the retaining wall, the ninfei and the underground and above-ground hydraulic conduits. Multiple survey campaigns have resulted in a highly detailed 3D model that supports restoration planning for reactivating the water displays.

In parallel, the CNR-ISPC in Florence has initiated diagnostic investigations to monitor the conservation state of the structure. In 2024, environmental sensors were installed to measure temperature and humidity in real time, and extensometers to monitor the stability of the masonry structures will follow. Geometric models and dynamic data have been integrated jointly by UNIFI, CNR-ISPC (Florence and Lecce offices) and the Regional Directorate of Museums through the SENNSE platform (Spatial Heritage Science Online Sensor Environment), created by the CNR-ISPC’s DHILab.

Today, the model functions as a Heritage Digital Twin, enabling targeted maintenance interventions, remote control of the water features and enhancement of inaccessible spaces. The grotto thus becomes a narrative device for interpreting its defining element: water. Through the digital twin, it is now possible to trace the historical path of water, understand its transformations, and document the material and intangible heritage of this extraordinary sixteenth-century hydraulic machine.