Crimea is semi-autonomous. It is part of Ukraine, but is self governed with many Russians living there. However, Ukraine was "gifted" Crimea by the Soviet Union in the 1950s. The location on the Black Sea makes it a desirable location and why Russia wants it in the first place.
This all has happened in the days after the close of the Sochi 2014 Winter Olympics. The Olympic Charter states, "the goal of Olympism is to place sport at the service of the harmonious development of humankind, with a view to promoting a peaceful society concerned with the preservation of human dignity." Yet they have intervened in the Ukraine with force, instead of letting the Ukranian people make their own decision. Its not like this is the first time the Olympic Charter has been called into question with regards to Sochi hosting. Speaking of Sochi, after spending a record $51 Billion on the Olympics, one has to wonder how much use they'll actually get out of everything they built in Sochi. With mild/warm weather even during winter, how many winter sports events will Sochi attract?