Dalhousie Square, or BBD Bag (expandable to Binoy-Badal-Dinesh Bag after the three young revolutionaries who stormed the Writers&rsquo Buildings in 1930 and shot the Inspector General of Prisons, N.S. Simpson), has been the heart of Calcutta long before the city became Kolkata. The centre of trade and commerce, its bylanes are full of cubbyholes from where all sorts of businesses are conducted. Though one might miss it &ndash disoriented by the chaos all around &ndash the Dalhousie Square area also has some of the most stunning buildings from the Raj era. The Writers&rsquo Buildings complex is one, to begin with. Dalhousie Square is the gateway to north Kolkata, and the nearby buildings and streets have many tales to tell. Explore this zone with a heritage walk.