Complex sentence: The Hôtel Raphael was the hotel of "le Bal" in 2013 and 2014 and the event was held in the Palais de Chaillot in 2015, overlooking the Eiffel Tower.
Split into simpler sentences: The Hôtel Raphael was the hotel of "le Bal" in 2013 and 2014. Le Bal was held in the Palais de Chaillot in 2015, overlooking the Eiffel Tower.