After the Berlin Wall fell in 1989, for a while it seemed like border fences and barriers were a thing of the past in Europe. Many on the continent hoped for a new era of integration and receptivity. It didn't happen. Instead, various pressures have led Europe to adopt wall-building projects that would make Donald Trump proud.

This summer Hungary drew international criticism for a 109-mile-long barbed wire border fence along its southern frontier with Serbia – a project made bitterly ironic by Hungary's 1989 decision to cut its border fence with Austria and help break the Iron Curtain. Hungary hoped that this fence would stem the flow of migrants and refugees traveling through Hungary on what has been referred to as the West Balkans route into the European Union.

Many outsiders were appalled. "We have only recently taken down walls in Europe," European Union spokeswoman Natasha Bertaud said when news of the fence spread in June. "We should not be putting them up."

Despite the outrage, Hungary's wall was apparently a success. Not only did the country extend its fence along its border with Croatia, other countries appear to be following its example. Slovenia has also proposed a fence along its border with Croatia, and Austria has taken the more remarkable move of beginning to build a fence along parts of its border with Slovenia – a move which would mean that a fence had been built inside Europe's border-control-free Schengen Area.

One police chief even suggested that Germany needed to build a fence along its border with Austria, although he was swiftly criticized by Chancellor Angela Merkel's office.

Hungary wasn't the first European nation to build a wall in recent years. This summer, Bulgaria announced its own plan for a border fence that will eventually span 100 miles of its border with southern neighbor Turkey, although Reuters notes that migrants and refugees continue to enter the country at an unprecedented rate. Bulgaria's wall sits not too far from a wall built by Greece in 2012. This wall, constructed with the intent of keeping out migrants and refugees crossing from Turkey, pales in comparison to the more recent walls. It covers just 6.5 miles of land border with Turkey (barriers were put up along the Evros River as well) and failed to stop the growing number of migrants who reached Greece by boat.

In the French town of Calais, the British government recently spent $10 million to erect improved fencing around the Channel Tunnel, a train link between France and Britain that has recently attracted relatively large numbers of migrants. Pascal Aerts, who leads the police assigned to the migrants in France, told the BBC that the fences would only push the problem elsewhere, most likely to ports in the Netherlands and Belgium. Barriers around the Spanish enclaves of Ceuta and Melilla in Morocco, significantly expanded in 2005, have done little to stem Europe's overall migrant issues.

The walls going up in Europe aren't all about migrants and refugees. In Ukraine, an enormous, $250 million plan to seal the 1,200-mile-long border with Russia is born of fear of Moscow's destabilizing influence. Estonia has also pledged to build a fence along almost 70 miles of its border with Russia.

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