Howrah is the second largest city of West Bengal. It is a major industrial and commercial center and the main rail and road hub of Kolkata. The Howrah bridge (Rabindra Setu) across the river Hooghly, connecting Howrah and Kolkata, is said to be the busiest bridge in the world. The Indian Botanic Gardens, Howrah is home to one of the world's largest banyan trees. The city is extremely congested and the novel "City of Joy" (Ananda Nagari) is based on one of its numerous slums. There are many multistoried apartment buldings in the city.