'The Vampire Diaries' Celebrates Milestone 100th Episode: Ian Somerhalder Goes on a Radio Tour Around U.S. to Talk about It [WATCH VIDEOS]

"The Vampire Diaries" (TVD) recently celebrated its milestone 100th episode which was shown on the CW Network on Thursday, Jan. 23, 2014. As part of the promotions of the hit show, TVD actor Ian Somerhalder who plays the vampire Damon Salvatore, went on a radio tour around the U.S. to talk about it.

Somerhalder excitedly tweeted about "The Vampire Diaries" 100^th episode and invited his Twitter followers to watch it along with the TVD cast.

He also tweeted about the aforementioned radio tour around the U.S. to promote the 100^th episode of TVD. Unfortunatley he didn't mention which cities or radio stations he will visit to talk to the DJs there.

The milestone 100^th episode of the popular vampire TV series which was adapted from the novels of author L.J. Smith, is titled "500 Years of Solitude." This very special episode was directed by Chris Grismer. It was written by Julie Plec and Caroline Dries.

"500 Years of Solitude" is the 11^th episode of TVD's Season 5. According to TV by the Numbers, this particular episode had 2.72 million viewers and had a 1.2/3 rating on the Thursday, 8 pm slot. More viewers watched this milestone episode compared to the 10^th TVD episode titled "Fifty Shades of Grayson," (air date: December 12, 2013, Writer: Caroline Dries, Director: Kellie Cyrus) which only had 2.44 million viewers.

The "500 Years of Solitude" episode showed vampire Katherine Pierce, whom Somerhalder refers to as Katherine Fierce, on her death bed, still plotting on how to cheat death and extend her life. She managed to trick Elena Gilbert, her doppelganger, played by Ian's ex-girlfriend Nina Dobrev. She convinced Elena to be there for her as she breathed her last breath, and then completed the Traveler possession spell which allowed her to switch bodies with someone else.

Now, she is in Elena Gilbert's body, unbeknownst to Damon Salvatore and company. Only her daughter Nadia knows about it. As for Elena, she's still inside her own body, it's just that now she has Katherine Pierce inside her too!

Aside from Somerhalder's radio tour around the U.S. to promote TVD's milestone 100^th episode, CW Atlanta also celebrated it by releasing 100 black balloons inscribed with the words "100th Anniversary, Vampire Diaries." They also held a live Twitter party during the airings of the episode on the West and East Coasts of U.S. The cast of "The Vampire Diaries" as well as the show's producers tweeted with the fans of TVD and answered questions from them.

Click HERE to see photos of the cast, crew, creator, writers and producers of CW's "The Vampire Diaries" TV series.

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