As one of the world's great centres of trade, the port of Liverpool developed a dedicated office district from an early date. In the 1780s, lettable offices were built by the Corporation near the Georgian Exchange (later known as the Town Hall), making possible the separation of home and workplace. The creation of the public square called Exchange Flags, and the erection of the first Exchange Buildings (1803–08), led to the rapid concentration of business activity in the surrounding streets. Early buildings combined offices with warehousing, but changes in the cotton trade resulted in their replacement with offices only. The first major speculative block was India Buildings (1833), and its success heralded a wave of rebuilding from the 1840s to the 1860s. Many office developers were merchants, but banks and insurance companies also incorporated lettable space into their premises. Classical styles predominated, but traditional fenestration was modified to ensure good natural lighting. The result was an exceptionally imposing business district, symbolising the immense commercial importance of Victorian Liverpool.