Twelve hours, twelve Apostles, one shadow and one rock. An iconic dome in Rome. Around the inside of this dome is written, in letters 2 metres high:

TV ES PETRVS ET SVPER HANC PETRAM AEDIFICABO ECCLESIAM MEAM.

meaning in English:

("...you are Peter, and on this rock I will build my church. ... ")

The name Peter is "Petrus" in Latin and "Petros" in Greek, deriving from "petra" which means "stone" or "rock" in Greek. But in French, "stone" or "rock" is "roche" or "pierre". So in French, it fits perfectly:

("...Tu es Pierre et sur cette pierre je construirai mon Église..." )

The English title is "Rock and Rome", but in French, the title would have been "Sainte pierre de Rome".

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The St. Peter's Basilica is traditionally the burial site of its titular. It is believed by this long tradition that Peter, after a ministry of about thirty years, traveled to Rome and met his martyrdom there in the year 64 AD during the reign of the Roman Emperor Nero. His execution was one of the many martyrdoms of Christians following the Great Fire of Rome. According to Origen, Peter was crucified head downwards, by his own request. The crucifixion took place near an ancient Egyptian obelisk in the Circus of Nero. The obelisk now stands in Saint Peter's Square and is revered as a "witness" to Peter's death. It is one of several ancient Obelisks of Rome.

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The sundial text is

GROW OLD ALONG WITH ME 
THE BEST IS YET TO BE

and the letters SP stand for either Simon Peter or Saint(e) Pierre. Only the shadow of the initials is shown to best fit the overall theme.

Indeed, whatever way we put it, physically or spiritually, a shadow always tells us about the direction of light.