Complex sentence: Miss Earth 2015 will be the 15th edition of the Miss Earth pageant to be held on 5 December 2015 at the Marx Halle, Neu Marx, Vienna, Austria.
Split into simpler sentences: Miss Earth 2015 will be the 15th staging of the Miss Earth pageant. It is to be held on 5 December 2015 at the Marx Halle, Neu Marx, Vienna, Austria.