Roman Sundial

• The Roman sundial was either a semicircular dial or a concave hemispherical surface with a nodus that measured the sun’s shadow.

Earliest Sundial in Rome

• Pliny the Elder recorded that the first Sundial appeared in Rome in 293 BCE.

Giant Sundial

• In 10 BCE Augustus built the giant Solarium Augusti using the giant Obelisk of Montecitorio, now in the Piazza de Montecitorio, to cast a shadow to tell the time.

Portable Sundials

• The Romans made small sized portable sundials which had a scale for adjusting to the user’s latitude.

Vitruvius

• Vitruvius in Book IX of De Architectura lists all known types of Sundial.

Obelisk of Montecitorio, Piazza di Monte Citorio