French officials unveiled an underground storm water facility in Paris that was built to clean up the Seine River ahead of this year's Olympics and Paralympics.

The facility, which is 50 meters in diameter and 30 meters in depth, was opened to the media on Thursday. It is located at the heart of the capital near the river.

The river will be the site of several events during the Games in July, August and September including triathlon and marathon swimming.

But Paris officials say sewage facilities in the city are too old to deal with storm water and thus floodwaters flow into the Seine. Critics have said the river's water quality needs to improve.

Officials say the new water storage facility is scheduled to become operational as early as this month.

The new facility can temporarily store up to 50,000 cubic meters of rainwater and other waters -- enough to fill about 20 Olympic-sized swimming pools. They say it will then pump and send the water to a sewage treatment plant.

The Paris government also plans to arrange a water purification facility in the upper reaches of the river and set up swimming areas at three locations in the summer of 2025.

Paris Mayor Anne Hidalgo said at the new facility's inauguration ceremony that it was a dream for people in Paris that they would be able to swim in the Seine again. She stressed that she wants to make the improvement of the water quality of the river a legacy of the Games.