In classical mythology, Cythera was the birthplace of Venus. Cronos the Titan castrated his father Uranus and threw his testicles into the sea. The sperm from them gave birth to Aphrodite/Venus, the goddess of love. She rose, fully formed from the waves and floated to the Mediterranean island of Cythera (Kythira). In legend, this island was the only place where perfect love could be found, so the pilgrims in the painting would be very sad to leave.
This reminded me of the aria Fairest Isle, All Isles Excelling from Henry Purcell's semi-opera King Arthur (1691). It is part of the final, celebratory masque to mark Arthur's victory against the Saxons and his love union with a Cornish princess. Merlin conjures up a vision of the isle of Britain, and in this song, Venus appears and sings of how Britain will become the new island of love, replacing Cythera:
Fairest isle, all isles excelling,
Seat of pleasure and of love;
Venus here will choose her dwelling,
And forsake her Cyprian grove.
Cupid from his fav'rite nation,
Care and envy will remove;
Jealousy that poisons passion,
And despair that dies for love.
Gentle murmurs, sweet complaining,
Sighs that blow the fire of love;
Soft repulses, kind disdaining,
Shall be all the pains you prove.
Ev'ry swain shall pay his duty,
Grateful ev'ry nymph shall prove;
And as these excel in beauty,
Those shall be renown'd for love.
(Lyrics by John Dryden)
This became a very popular song in the 18th century. In 1747, Charles Wesley published a hymn to the same tune which became a standard of the English-speaking church:
Love Divine, all loves excelling,
Joy of heaven, to earth come down,
Fix in us thy humble dwelling,
All thy faithful mercies crown.
Jesu, thou art all compassion,
Pure unbounded love thou art;
Visit us with thy salvation,
Enter every trembling heart.
It's easy to see how the first verse mirrors the first verse of Dryden and Purcell's song. In Wesley's hymn, perfect love cannot be found with Venus, but in the love of God and the Lord Jesus for the human soul. This love comes down to earth and the human heart from heaven, in the same way as Venus comes from Cythera to live in Britain in the original song.
This hymn remains extremely popular, although it's not usually sung to Purcell's tune any more. (In Britain, it's usually sung to a tune called Blaenwern). It was number 14 in the BBC Songs Of Praise most popular hymn poll, 2013. Ironically, one of the reasons it is so popular is because it is used so much at weddings. It is listed on the Church of England's yourchurchwedding.org as one of the most popular wedding hymns. It seems that couples are hoping the "love divine" will bring them their own version of Cythera.