For The 500 Hidden Secrets of Copenhagen Austin Sailsbury went looking for the most wonderful places to be in the Danish capital ; like a smørrebrød spot in the Torvehallerne food market that serves fresh ; creative open-face sandwiches made right in front of you ; a tiny arched tunnel which ; every three to five weeks ; is reclaimed by an artist who covers the walls with his or her own vision ; or an urban development where housing units were built atop a sloping concrete parking structure ; thus allowing for an artificial mountainside below and cascading ; terrraced apartments high above street level.