Eugene Delacroix, Death of Sardanapalus, 1827. Oil on canvas, 12' 1" x 16' 3."
I'm not a huge fan of Romanticism, but I thought the two best paintings at the Louvre were Delacroix's Death of Sardanapalus and Gericault's Raft of the Medusa (which will most likely turn up in a later installment of "Paintings I Like").
The scene in this painting is from a play by Lord Byron called Sardanapalus, which tells the story of an Assyrian king who orders his entire city burned and all its inhabitants killed rather than turning it over to an invading army. At the end of the play, Sardanapalus sets himself on fire. Sardanapalus may or may not have actually existed.
Vaguely to overtly racist "Arabian" themes were immensely popular in 19th-century French painting well past the Romantic era (paintings of this sort drew the scorn of the Impressionists and Van Gogh). Not surprisingly, exotic pin-up girls routinely played a role in pieces from this genre. All of that said, this painting is still a full-fledged masterpiece.
There is no floor that I can identify - just writhing figures, anchored by that big red bed and the bizarrely calm Sardanapalus. The only thing in the picture that resembles a straight line is the gaze from the king to the concubine in the foreground pleading for her life - the two most well-lit areas of the painting. Delacroix was probably the best colorist of the Romantic period, and clearly absorbed a great deal from the Venetians: the intervals of deep red in the areas of highest drama and the hazy atmosphere in the upper right and lower left are very much informed by that style.
The size was what really gave it magnificence. I'd seen the painting in reproduction many times before actually seeing the original in the Louvre, but was completely unprepared for the real article. It's like a Cecil B. DeMille period movie - it really only works on the Big Screen.