"We are in the trash time. We produce trash and we will be trash. So this hotel is the mirror of the situation," Schult told AFP on Friday, on the eve of World Environment Day.
About the size of a large single family house, the temporary hotel -- open from June 3 to 7 -- stands in the shade of Rome's Castel Sant'Angelo, a second century landmark castle along the banks of the Tiber river.
The building is completely covered on all sides with old tins, hats, cameras, socks and soccer balls found on European beaches and selected by Schult.
"In the ocean, the trash from all continents meets one another. The trash from Africa meets the trash from Europe, meets the trash from South America," Schult said, pointing to the guitars and shoes plastered across the building.
"The environmental problem is a global problem. We are living in a planet of garbage," said Schult, whose most famous work is "Trash People," an installation of 1,000 human figures made out of trash.
"Trash People" was installed under the Brooklyn Bridge in New York, in front of the Giza Pyramids in Egypt, in Red Square in Moscow, at La Defense in Paris, and along the Great Wall of China.
Danish supermodel Helena Christensen slept in the three-room, two-bathroom hotel to raise awareness about the trash polluting the world's beaches.
"You walk down the beach and you realize how incredibly ignorant we are with garbage," Christensen said.
"It was fun. I've slept in worst places," said Allan Thompson, a 53-year-old from London, who spent Thursday night in the hotel along with his daughter.
"Some of that stuff goes way back, it doesn't go away," said Thompson, who won a night's stay at the hotel when he entered a competition to win a years' worth of Corona, the Mexican beer that sponsored the work.
Schult has been shining a spotlight on garbage since the 1960s, but is now increasingly concerned about the mountains of trash now coming from high-growth countries like China and India.
"We have to change the world, before the world changes us," he said.