The mesh-like fossil would push back the oldest known animal on Earth by more than 300 million years. But like many claims of very old life, the study is kicking up lively debate.

Rasmussen says Copenhagen has transformed 20 green areas like Enghaveparken into what the city nicknames "sponge parks." When full, he says, Enghaveparken can hold 25,000 cubic meters of water.

In addition to the sponge parks and cloudburst tunnels, Copenhagen has also just broken ground on a human-made island off its coast, named Lynetteholm. The island will house 35,000 people and protect ...

In addition to the sponge parks and cloudburst tunnels, Copenhagen has also just broken ground on a human-made island off its coast, named Lynetteholm. The island will house 35,000 people and protect ...

Rasmussen says Copenhagen has transformed 20 green areas like Enghaveparken into what the city nicknames "sponge parks." When full, he says, Enghaveparken can hold 25,000 cubic meters of water.