Singapore's Gardens by the Bay has opened, and the star attractions are some of the most unnatural-natural structures viewers are likely to see.

The gardens feature a host of vast steel trees between 25 and 50 metres high, connected by walkways, and containing hundreds of varieties of real plants.

The "supertrees" light up at night, using solar energy collected during the day to power the display, in a mirroring of nature, as architect Andrew Grant explained: "Real trees, they generate energy from sunlight, that's one of their key functions, they produce oxygen, they are fundamental to the world and life.

"And here in the supertrees, one of the big things was to actually take cells onto the tops, which produce energy, which help contribute to the overall energy load of the project."

Over 10,000 people packed into the gardens for an opening concert by singer Jason Mraz.

The Gardens by the Bay is set to be one of the largest manmade arboretum attractions in the world.