Castle Walls (feat. Christina Aguilera)

This is the second single by American rapper T.I., from his seventh studio album, No Mercy. The reflective song was produced by Alex Da Kid and features pop-singer Christina Aguilera.

The song finds T.I. rapping about the downside of fame despite all he has achieved, whilst in Aguilera's hook the singer complains that regardless of all she has in life, she still gets lonely: "Everyone thinks that I have it all/ But it's so empty living behind these castle walls (These castle walls). " This might be a reference to Aguilera filing for divorce from her husband music marketing executive Jordan Bratman on October 14, 2010. It could also refer to T.I.'s extended time in jail. No Mercy was the Atlanta MC's first release since being freed from prison where he served a sentence on weapons charges. Two days before No Mercy came out, he begun another stint in the slammer for parole violations.

British producer Alex Da Kid is best known for co-writing both Eminem's hit single "Love The Way You Lie" and Rihanna's sequel, "Love The Way You Lie (Part II)." He gushed to MTV News about this mellow track. "I love it. I think it's amazing. It's my sound, just kind of an evolution of that. I think it'll cater to a lot of different people."