Severn Trent Water has been fined £500,000 for discharging thousands of gallons of raw sewage from its sewer network onto land at Sutton Park, Birmingham in November 2013.
The company was also ordered to pay prosecution costs of £50,693.97 and a victim surcharge of £120.
The visitor centre received complaints of sewage smells and a park ranger found a large amount of sewage flowing from a manhole cover and spreading across the surrounding area.
The sewage had spread across an area bigger than an international rugby pitch. Sewage had also got into Longmoor Brook and Longmoor Pool within the Park.
During sentencing the judge said that although the clean-up operation had been slow and poorly managed, that the company had ultimately taken all necessary steps to clear up the park and that it had made a long term commitment to restoring the affected area.