Tsarevich Nicholas Alexandrovich Romanov was born on September 20, 1843, at Alexander Palace at Tsarskoye Selo and died on April 24, 1865, at Villa Belmont in Nice, France.

He was the eldest of six sons and the second of the eight children of Alexander II, Emperor of All Russia and Princess Marie of Hesse and by Rhine (Empress Maria Alexandrovna). In 1864, Nicholas was to visit the Danish Royal Family at Fredensborg Palace during a European tour. He had fallen in love with Marie Sophie Frederikke Dagmar of Schleswig-Holstein-Sonderburg-Glücksburg, known as Princess Dagmar and called “Minnie” in her family, who was born in Copenhagen, Denmark in 1847. During an afternoon walk on September 28, 1864, Nicholas proposed to Dagmar and she accepted. He then continued his European trip.

On January 1, 1865, Nicholas traveled to Nice, France, where his mother was spending the winter. On April 17, 1865, Nicholas suffered a cerebral hemorrhage leaving one side of his body paralyzed. Six doctors determined that Nicholas had cerebrospinal meningitis and that his condition was very serious. He died on April 24, 1865, at the age of 21 at Villa Belmont, in Nice, France.

Nicholas’ parents bought the grounds and villa in which their son had died. They tore down the villa and built a memorial chapel and statue -as the photo shows- in the exact location where his deathbed had been. The Cathedral of St. Nicholas was built opposite to the memorial by his nephew, Tsar Nicholas II in 1912.

More Info: en.wikipedia.org