One tunnel is about 50 feet long, unfinished, and stretches across two countries. It starts along the drainage channels that a U.S. border town shares with Mexico, and abruptly ends underneath a parking lot in Arizona. Another one runs about 80 feet, also unfinished. Its opening was found inside an abandoned store in the Mexican border city of Nogales. A third one is about 30 feet, also found somewhere in Nogales, though it’s unclear where it starts or ends. These tunnels, which authorities suspect were built to smuggle illegal contraband or people across the border, were found within the past month, as President Trump continues to demand $5.7 billion to build a border wall between the United States and Mexico. The stalemate over Trump’s signature campaign promise has resulted in what is now the longest government shutdown in the country’s history, leaving thousands of federal workers without pay. The president has argued that building physical barriers would stave off illegal immigration and drug trafficking into the United States. But experts say these tunnels reaffirm a reality at the southern border: Drugs are trafficked into the country through multiple channels, including underground. A physical barrier, whether it’s fencing, steel slats or a concrete wall, would keep out people who are willing to play by the rules. But for those who aren’t or can’t afford to, walls are mere temporary inconveniences, said David Shirk, an international relations professor at the University of San Diego.