Prostitution is legal in India, but a number of related activities including soliciting, kerb crawling, owning or managing a brothel, prostitution in a hotel, child prostitution, pimping and pandering are illegal. There are, however, many brothels illegally operating in Indian cities including Mumbai, Delhi, Kolkata, Bangalore, and Chennai. UNAIDS estimate there were 657,829 prostitutes in the country as of 2016. Other unofficial estimates have calculated India has roughly 3–10 million prostitutes. India is widely regarded as having one of the world's largest commercial sex industry. It has emerged as a global hub of sex tourism, attracting sex tourists from wealthy countries. The sex industry in India is a multi-billion dollar one, and one of the fastest growing. A tawaif was a courtesan who catered to the nobility of India, particularly during the Mughal era. The tawaifs excelled in and contributed to music, dance (mujra), theatre, and the Urdu literary tradition, and were considered an authority on etiquette. Tawaifs were largely a North Indian institution central to Mughal court culture from the 16th century onwards and became even more prominent with the weakening of Mughal rule in the mid-18th century. They contributed significantly to the continuation of traditional dance and music forms and then emergence of modern Indian cinema. Goa was a colony in Portuguese India set up in the early 16th century, and this Portuguese stronghold contained a community of Portuguese slaves. During the late 16th and 17th centuries the Portuguese trade in Japanese slaves resulted in traders from the Portuguese Empire and their captive lascar crew members from South Asia bringing Japanese slaves to Goa. These were usually young Japanese women and girls brought or captured from Japan as sexual slaves. The culture of the performing art of nautch, an alluring style of popular dance, rose to prominence during the later period of Mughal Empire and the rule of the British East India Company.