You can see it clearly in the picture of Cirey on the old "Voltaire" ten-franc banknote.
The inner arch is elaborately decorated with seashells and features two very fine sculpted heads of the god Neptune, one awake and one asleep. It is often said that the marine theme reflects the ideas of Maupertius, Voltaire's rival in love, who thought that the origins of life were to be found in the sea. This may be an over-interpretion; the staircase inside boasts almost equally effusive fruit-baskets. Professor Saget also notes a very similar sculpture on a doorway in the rue de Varenne; probably this one on the Hôtel Gouffier de Thoix, no.56:
Above the arch Voltaire has placed an inscription from the Bucolics of Virgil, "Deus nobis haec otia fecit", "God has given to us this leisure", an allusion to the enforced idleness of his stay in Cirey.
LEFT PILLAR (TOP TO BOTTOM)
1. A terrestrial globe with meridians, and a telescope - possibly a reference to Madame du Châtelet's astronomical interests.
2. A set-square, compass, plumb line - again an intellectual allusion or freemasonry signs?
3. Two vines. These correspond to a human head on the right pillar - signifying perhaps "man in the face of Nature".
4. Another Latin phrase, this time taken from Horace
"Hic virtutis amans, vulgi contemptor et aulae
Cultor amicitiae, vates latet
"Here the poet, who loves virtue and scorns the crowd and the Court, cultivates friendship, remaining hidden in rural retreat"
5. An inkwell and pen symbolising literature.
6. Famous lines of Voltaire own composition:
"Azile des Beaux-Arts, solitude où mon coeur
Est toujours demeuré dans une paix profonde
C'est vous qui donnez le bonheur
Que promettait en vain le monde"
“Refuge of the fine arts, solitude where
/in a deep peace I left my heart
You gave me the happiness
That the world promised me in vain”
RIGHT PILLAR (TOP TO BOTTOM)
1. Globe with a set square, perhaps signifying moral rectitude.
2, Palette and brushes, symbolising painting
3. A human head.
4. Mallet and scissors, for sculpture.
5. Is there something else here? Prof. Saget doesn't say and I can't make it out.
6. Inscription in English:
"When dulls prevail and hypocrisy bear sway
The post of honour is a private station"
This is taken from Act iv of Joseph Addison's play Cato. ( Voltaire slightly misquotes - perhaps deliberately;Addison has, "when vice prevails and impious men hear sway". Not sure "dull" is really an English noun.)
Hubert Saget, Voltaire a Cirey, (2nd ed 2005) p.146-50.