Medieval and Renaissance Madonnas will no longer risk their vibrant blue mantels turning into yellowish grey robes, according to U.S. researchers who have discovered why natural ultramarine blue sometimes fades in frescoes.

Known as "ultramarine sickness," the irreversible form of discoloration has been observed in frescoes at the Church of Saint Augustine in San Gimigniano, near Siena, and in the Basilica of Assisi.

"Our studies explain for the first time the process of fading in ultramarines and may lead to the design of proper art conservation treatments and the development of more-permanent pigments..."

The use of this colour was usually reserved to artworks of great importance, such as the funeral mask of Tutankhamen. The pigment found its most extensive use in 14th and 15th century Italian paintings, and was often reserved for the robes and mantels of Christ and the Virgin Mary...

Study Reveals Why Blue Frescoes Fade, Rossella Lorenzi, Discovery News, USA, October 13, 2006.

Cairo has long been a favourite with holidaymakers wanting to discover the Pyramids of Giza, and offers a host of cultural attractions besides.

The Old Cairo and Islamic Cairo areas will keep you entertained for hours as you navigate the narrow streets and discover the hidden mosques, churches, museums and souks.

The main market is the Khan al-Khalili, where you'll find yourself haggling for silk and spices and the many outdoor cafes provide the perfect place to rest weary legs and do a spot of people-watching...

Cairo is a strong cultural draw, Go Travel News, UK, October 16, 2006.