Nan told Bill in S4E2 about Luis Pasteur being a vampire. Blue ray extras gave this addition information:
Louis Pasteur, born in 1822, was a French chemist and microbiologist hailed for his invention of what is now known as pasteurization. He also made immense gains in the fields of disease prevention and vaccination. He supposedly died in September of 1895, with the general public believing his remains to be six feet under the Institute Pasteur in Paris, his tomb decorated with Byzantine mosaics illustrating his many achievements.
I did a little search and it is true that the style of the art in the crypt is Byzantine (among other symbolism) as Pasteur died having a genuine faith even though he was a scientist.
The architect designing the crypt was Charles-Louis Girault.
Yet another clue to Byzantine Empire.