Tsar Alexander I declared his intention to build a Cathedral in honor of Christ the Saviour after Russian victory in war with Napoleon in 1812. Tha Cathedral was buit as a memorial to the sacrifices of the Russian people. However it took many years before Cathedral emerged from its scaffolding in 1860. Best Russian artists continued to embelish it´s interior for another twenty years.
After the Revolution the site of the cathedral was chosen by the Soviets as the site for a monument to socialism known as the Palace of Soviets.
On December 5, 1931 the Cathedral of Christ the Saviour was dynamited and reduced to rubble. It took more than one blast to destroy the church and more than a year to clear the debris from the site. The construction of the Palace of Soviets was interrupted due to a lack of funds, problems with flooding from the nearby Moskva River, and the outbreak of World War II. Later it was transformed into a huge public swimming pool, the largest the world has ever seen.
With the end of the Soviet rule, the Russian Orthodox Church received permission to rebuild the Cathedral of Christ the Saviour in February 1990. The completed Cathedral of Christ the Saviour was consecrated on the Transfiguration day, August 19, 2000.

Sources, related links:
Adapted from: Wikipedia - Cathedral of Christ the Saviour (Moscow)
Official web site of The Cathedral of the Saviour