Overview: Historian and writer Dan Cruickshank celebrates architecture as a creative force as he explores the world's greatest cities, buildings and monuments. Dan sets out to reveal how architecture enables people to live together across the world. He finds vibrant communities in extraordinary buildings - but why do some places succeed and others fail? To find out, Dan visits Brasilia, an ideal city built by communists, the Rockefeller Centre in New York and Dharavi in Mumbai, the biggest slum in India.