Rosslyn Chapel

The 'secrets' come down to the sheer density and detail of the stone carvings, which have fuelled centuries of speculation about Templar links, hidden treasure and the Holy Grail. Dan Brown's The Da Vinci Code brought those theories to a global audience, though historians point to the chapel first as a remarkable piece of 15th-century Gothic craftsmanship.

The Da Vinci Code, released in 2006 and starring Tom Hanks, featured the chapel prominently in its closing scenes and sent visitor numbers sharply up.

The chapel is dedicated to St Matthew and was built as a collegiate church by William Sinclair, 1st Earl of Caithness, in 1446. Its carvings are thought to carry spiritual and symbolic meaning, though scholars still debate quite what.

The original plans were far grander, intended as a much larger cruciform church. Work stopped after William Sinclair died in 1484 with only the choir complete, and the planned transepts and nave were never built.