In The 500 Hidden Secrets of Barcelona Mark Cloostermans shares 500 must-know addresses in the capital of Catalonia ; such as one of the best seafood restaurants in town where all customers sit at the bar and the team prepares the food as you watch ; a Benedictine monastery that was (re)built and destroyed multiple times and now serves as an oasis of other-worldly calm amid the neighbourhood buzz and a square with a sad past that now is a haven of piece in a tourist-heavy zone.