Perhaps one of the most unqique attractions across Europe is the opportunity to go beneath the streets of Paris to walk the claustrophobic, muddy pathways of its catacombs. Not for the younger children, or the faint at heart, this attraction appeals to ‘tweens and teens and those with a morbid curiosity. When the plague ravaged Paris, the cemeteries were overflowing and fear forced the city to put the dead in its catacombs. More than six million were buried in the catacombs in the 18th century, now bones are piled neatly and actually artistically from floor to ceiling. Children under 13 who can take it are welcome free.