Trump suggested building a wall across the Sahara. Photo: Stefano Montesi/Corbis via Getty Images

Donald Trump is not having much luck getting his “big, beautiful border wall” off the ground, with his own party refusing to fund the vanity project that would be wildly ineffective and way too expensive. But that hasn’t stopped him from suggesting other countries take a shot at building their own.

Spanish foreign minister Josep Borrell revealed this week that Trump proposed Spain build a wall across the Sahara to stem the flow of migrants into Europe. When diplomats brushed aside the idea and pointed out that the desert is 3,000 miles long, Trump pushed back. “The Sahara border can’t be bigger than our border with Mexico,” he reportedly said. It is, in fact, bigger.

Trump is thought to have made his suggestion to Borrell in June, when the foreign minister visited the U.S. along with Spain’s king and queen. Borrell reportedly made his opposition to the idea clear at the time, but did acknowledge that Spain must do something about the migrants coming to the country.

Already this year, more than 38,000 migrants have arrived in Spain, most by sea. The Guardian reports that this three-fold increase over last year makes Spain the most popular destination for migrants, surpassing Italy and Greece.

And while Borrell brushed off Trump’s wall suggestion, Spain does see fit to keep out some would-be immigrants with border fences. The Spanish cities of Melilla and Ceuta are each separated from Morocco by parallel 20-foot fences topped with razor wire. But not even those keep everyone out.