Hidden Cardiff: What secret is behind burger bar door?
For the thousands of people visiting Cardiff over this Champion's League final weekend - the best kept secrets of the city have been under their feet.
Hidden canals wind their way under the main shopping centre in Cardiff, while beneath the fan campsite in a city centre park there lies a medieval friar's tunnel, its entrance just a couple of foot high.
Explorer Will Millard, who previously focused on more exotic locations, has discovered some of the hidden parts of Cardiff as part of a new BBC programme.
He was introduced to one of his most spectacular finds by city historian Peter Finch - hidden behind the staff only door of a well know burger bar.