Mexican authorities found last week a suspected drug-smuggling tunnel in Tijuana so deep that they haven't been able to find the exit point due to a lack of oxygen tanks.
While the discovery garnered attention for being the first of the year, other similar constructions have been found by law enforcement throughout the years, some of them also featuring similar lengths and depths. In fact, close to 20 tunnels have been found on California's border with Mexico since 2006, according to CBS News.
