On of the most extravagant buildings was the construction of to Crystal Palace in London, which was made out of iron and glass. It was a great symbol of the modern era. But between 1750 and 1851, the population increased dramatically. It did this because many families moved to cities to find work elsewhere. So the industry was growing, more people were steadily moving to the cities, and the population increased rapidly.
Factory owners demand more and more housing for their employees.
Since it had to be built to keep up with all of the newcomers, most of it was built very clumsily and cheaply. The housing was dark and badly ventilated. They were built in very cramped conditions, back to back in long rows. The really poor ones had only a basement or outhouse to live in. The meant unemployed and orphans were forced to fend for themselves on the streets.