In classical Roman religion, a genius loci (plural genii locorum) was the protective spirit of a place. It was often depicted in religious iconography as a figure holding attributes such as a cornucopia, patera (libation bowl), or snake. Many Roman altars found throughout the Western Roman Empire were dedicated to a particular genius loci. The Roman imperial cults of the Emperor and the imperial house developed in part in connection with the sacrifices made by neighborhood associations (vici) to the local genius. These 265 local districts had their cult organised around the Lares Compitales (guardian spirits or lares of the crossroads), which the emperor Augustus transformed into Lares Augusti along with the Genius Augusti. The emperor's genius is then regarded as the genius loci of the Roman Empire as a whole.
Roman examples of these genii can be found, for instance, at the church of St. Giles, Tockenham, Wiltshire, England, where the genius loci is depicted as a relief in the wall of a Norman church built of Roman material. This shows "a youthful and curly-haired Roman Genius worked in high relief, holding a cornucopia in his left hand and a patera in his right", which previously has been "erroneously identified as Asclepius".
The numinous spirits of places in Asia are still honored today in city pillar shrines, outdoor spirit houses and indoor household and business shrines.
In contemporary usage, genius loci usually refers to a location's distinctive atmosphere or a "spirit of the place" rather than necessarily a guardian spirit. An example of contemporary usage might be "Light reveals the genius loci of a place."
Alexander Pope made the genius loci an important principle in garden and landscape design with the following lines from Epistle IV, to Richard Boyle, Earl of Burlington:
Consult the genius of the place in all;
That tells the waters to rise, or fall;
Or helps th' ambitious hill the heav'ns to scale,
Or scoops in circling theatres the vale;
Calls in the country, catches opening glades,
Joins willing woods, and varies shades from shades,
Now breaks, or now directs, th' intending lines;
Paints as you plant, and, as you work, designs.