The diamond-shaped main island, Singapore Island (Pulau Ujong) is 42km east to west, and 23km north to south. The downtown, or CBD, radiates out from the mouth of the Singapore River at the southern tip. Also in the south is Chinatown and the ultra-modern Financial District. Within 4km of the CBD lie the historical quarters including the Colonial District, Little India, Arab Street, and the famous shopping street, Orchard Road. Most people arrive in Singapore from Changi International Airport at the east side of the island and move about the island on Singapore's extremely efficient MRT metro or bus system.