The gold covered dome houses Napoleon's tomb. The gold is real, and was applied to celebrate the bicentenary of the revolution.
Napoleon's ashes were brought to Les Invalides from St. Helena on 15/12/1840. On 14/4/1861 they were moved to the crypt, where they were housed in a tomb designed by Visconti.
The tomb is six nested coffins, rather like a Russian doll. The ceremony was attended by Napoleon III.