Roald Dahl Plass

Roald Dahl Plass is a large public square, part of the Cardiff Bay district of Cardiff, Wales. It is a poorly-kept secret among many Cardiff residents that somewhere near the Plass is the site of the "secret" Torchwood organization's headquarters, The Hub (to the point where people asking about Torchwood are invariably directed to Roald Dahl Plass). (TW: Children of Earth: Day One)

The Plass is named in honor of a famous Welsh author of the 20th century.

History
It is unclear how long Torchwood has maintained its Hub headquarters below the Plass, though it is known to have been there since at least 1999 (TW: Fragments). Due to its proximity to a rift in space and time, the Doctor landed his TARDIS there in 2006 to "refuel". (DW: Boom Town) The perception filter of the TARDIS, which helped it blend into its surroundings, created a spot of perpetual perceptual blindness, enabling Torchwood to set up an "invisible lift" without anyone noticing it. (TW: Everything Changes) This lift provided an alternate entrance (and, occasionally, emergency exit) from the Hub, which otherwise was entered via a dockside entrance below the Plass. In 2008, the TARDIS returned to the same spot in the Plass, enabling Jack Harkness to jump onto it just before it dematerialised. (DW: Utopia)

Due to its proximity to the Hub, Torchwood kept the Plass under extensive surveillance. At one point a public area in the Plass was even used as the site for an erstwhile "job interview" for a prospective Torchwood 3 recruit. (TW: Children of Earth: Day One)

In September 2009, attempts by elements of the British government to cover up the first 456 incident, which had involved Harkness and Torchwood, resulted in a bomb being implanted within Harkness. The bomb detonated, destroying the Hub and causing massive damage to Roald Dahl Plass. As far as the public was concerned, the Plass was destroyed by a terrorist bombing. (TW: Children of Earth: Day One; Children of Earth: Day Two)

Behind the Scenes
In real life, the fact that Doctor Who and Torchwood have so prominently featured the Plass has made it a popular destination for fans visiting Cardiff. It is also one of the more public filming locations, so whenever the Doctor Who and Torchwood crews film there, it often attracts media attention (such as on 6 January 2010 when filming for Series 5 of Doctor Who took place there .)