An Industrial Park allows the addition of two Engineer specialists to your city, with an extra free Engineer thrown in for good measure. This comes at a significant cost to your city's health.
During the Industrial Revolution, newly industrialized cities became grossly polluted: thick smoke filling the air; industrial waste contaminating local bodies of water. This arrangement remained virtually unchanged through the first half of the twentieth century, and cities became increasingly unhealthy places to live.
One solution to this problem was to create specially zoned areas of industry - Industrial Parks. These parks took the harmful industries out of the population centers and centralized production facilities to increase efficiency.