The same castle in Cardiff was used for at least two episodes of “Doctor Who”. The Tenth Doctor, David Tennant,first used this location in season four, “Journeys End”.
Shortly after, Matt Smith, the Eleventh Doctor, arrived at the same location in season 5, “The Vampires of Venice”. Still, the castle is located in Cardiff, a long way from Venice….

http://cadw.gov.wales/daysout/castell-coch/?lang=en