Watch Barbie and the Diamond Castle (2008) HD Full Movie Free on SolarMovie. Watch Barbie and the Diamond Castle (2008) online free. Two best friends, Liana and Alexa, embark on a journey to find the Diamond Castle! With the help of ...Two best friends, Liana and Alexa, embark on a journey to find the Diamond Castle! With the help of music, the girls overcome challenges that show friendship is the true treasure.