A competition to find alternative designs to replace the destroyed Notre Dame Cathedral roof has attracted a number of innovative "solutions" – including a rooftop waterway over the medieval cathedral.

The People’s Notre Dame Cathedral Design Competition was launched in defiance of the French senate’s plans to restore the roof exactly as it was before the devastating fire earlier this year.

Set up by book publisher GoArchitect, the campaign invited architects to enter their designs for the new roof, "no matter how outlandish".

Launching the competition, GoArchitect urged the French government to consider all of the designs sent in.

“It would be a terrible loss to the democracy of design if the French senate closes the door to the debate and exploration of the future of Notre Dame,” said Joshua Sanabria, CEO of GoArchitect.

While most of the entries are – at least on paper – realistic, the competition also received some outlandish suggestions, exactly as the organiser wanted.

Perhaps the most unconventional was an entry sent in by "Bay Huynh Architects", who proposed an urban waterway to "explore the value of faith and society". The project was portrayed as an "intersection of internal and external traffic through the open-roof and flowing-fish lines".

The eventual winner of the competition – which, so far, has not been endorsed or even recognised by the French government – was the "Paris Heartbeat" project by Zeyu Cai and Sibei Li.

The pair's design replaces the iconic spire destroyed in the fire with a mirrored one, which would also include a time capsule – designed to be open every half century – at the summit.

To view all the entries – including the outlandish ones – click here for the competition homepage.