Doctor Who's Executive Producer and Head Writer Steven Moffat has been talking about a new episode of the series. He revealed details of the expected tenth episode of the 7th series - 'Journey to the Centre of the Tardis'.
The episode is set to explore further interiors of the Tardis, with little explored in the teleporting police phonebox before now, aside from the main control room. Many times has there been references to a swimming pool ('The Day of the Moon'), and we've even had a look inside the Doctor's walk-in wardrobe. (‘The Doctor, The Widow and The Wardrobe’)

In Los Angeles at the annual ‘Gallifrey One’ convention Moffat said,
“We've built the rest of the Tardis! The idea is in the title; we're going to journey to the centre of the Tardis. We've got some great visuals for that.”
Ashley Walters who guest stars in the episode as Van Baalen said: “In our episode it'll be the first time people get to see so much in the Tardis.” It is currently unknown who the character ofVan Baalen is.
The new interior is the work of production designer Michael Pickwoad, who in December 2012 gave the Tardis control room a modernised revamp; which got a positive reception from fans.
It has yet been revealed which parts of the Tardis will be seen in the upcoming episode.
The Doctor (Matt Smith) and his new companion Clara Oswin Oswald (Jenna Louise-Coleman) will return with the second half of the seventh series with an Easter special on Saturday 30th March on BBC One.
What would you have in your very own Tardis? Are you excited about the series returning?
the death of steven moffat might breathe new life into the galifrayen saga. Short of wishing ill on another let's hope he's merely fired soon
The article is not saying that there have not been beyond the main control room before. It is saying little has been explored. Moffat may mean the Matt Smith run. Hopefully this will become more clear.