This egg was made in 1901 and given by Tsar Nicholas II to his mother who lived in the Gatchina Palace..
It's made of white enamel and gold and is decorated with seed pearls on the outside.
Inside the egg is a miniature model of the Imperial Gatchina Palace, which can be removed from the egg. (see below):
As you can see, the tiny replica is made with fine precise detail. It has trees, flags and even a small statue of Tsar Paul I, who was the first Tsar to live in the palace. It's made of gold and silver-gilt, with the windows made of rock crystal.