Question: When were Napoleon I's remains interred in his mausoleum?
Sentence: They visited the Exposition Universelle (a successor to Albert's 1851 brainchild the Great Exhibition) and Napoleon I's tomb at Les Invalides (to which his remains had only been returned in 1840), and were guests of honour at a 1,200-guest ball at the Palace of Versailles.
Answer in sentence: yes