Three years before Germany invaded Poland in 1939, Adolf Hitler ordered the construction of the world's largest tourist resort, located on a beachfront property on the island of Rügen.

The Nazis called it Prora.

Hitler never finished construction on Prora due to the onset of World War II. As German soldiers marched through Europe, Prora was left to rot — until 2013.

Prora is now the property of German real-estate company Metropole Marketing, which rents out rooms to international travelers and Germans alike.

Here are a handful of insane facts about the mega-structure.

More than 9,000 workers helped construct Prora.

(Tobias Schwarz/AFP/Getty) (TOBIAS SCHWARZ/AFP/Getty Images)

Historian and tour guide Roger Moorhouse told Business Insider that Prora was intended as the carrot to the stick of the Gestapo — a pacifying gesture to get the German people on Hitler's side.

At the time, Germany was still enmeshed in the concept of “people's community,” or volksgemeinschaft, from World War I. It was a sense that Germans stood united, no matter what.

The structure was built to hold 20,000 people.

(Tobias Schwarz/AFP/Getty) (TOBIAS SCHWARZ/AFP/Getty Images)

While the Nazi police state was in development, the overarching German vision was a hopeful one, Moorhouse told Business Insider. “And this,” he said, “is where something like Prora comes in.”

Each room would measure 16 feet by 8.2 feet and include two beds, a sink, and a dresser.

In the centre of Prora, Hitler commissioned a festival hall large enough to hold all 20,000 residents at once.

Hitler's megalomania — a trait shared by many dictators — was also manifested in his plan for the Festival Hall. The Nazi leader commissioned architect Erich Putlitz to design it.

The hall would contain two wave pools and theaters for movies and live performance.

The entire building measures 2.8 miles long, and is located 150 yards from the beach.

(Jens Koehler/AFP/Getty) (JENS KOEHLER/AFP/Getty)

“The photos cannot physically do it justice,” Moorhouse said. “It's too big.” By all accounts, it would have been one of the most impressive structures in the world.

It also features the world's longest youth hostel, which contains 402 beds and 96 rooms.

In the early 2000s, several German developers fought for the initial rights to revive Prora.

In 2006, Germany's federal agency for real estate bought Block 5, which contained the hostel.

The hostel opened in 2011.

The largest units costs nearly $1 million to buy.

(Metropole Marketing (Metropole Marketing)

People who want to stay at Prora can choose between hotel rooms for temporary visits, and long-term investments in the form of luxury apartments.

The apartments run between $400,000 and $900,000 depending on the block in which they're located and the size.