The Anzob Tunnel in Tajikistan, Asia, also known as the "Tunnel of Death," is regarded as the darkest and most treacherous tunnel on the planet. Situated on the M34 highway at an elevation of 2,700 metres in the Tajikistan mountains, the 5km tunnel lacks lighting or ventilation systems.

The pitch-black tunnel is shrouded in dense smoke, making breathing "hard and painful due to the thick mixture of exhaust gases", according to specialists at Dangerous Roads.

The frightening underpass features massive potholes and lacks adequate lighting and ventilation, rendering it exceptionally hazardous.

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The Anzob Tunnel links Dushanbe, the nation's capital, and Khujand, the country's second-largest city, and was constructed in 2006 to accommodate heavy traffic, reports the Express.

There are also no traffic signals to manage the thousands of vehicles passing through it daily; instead, just complete darkness.

The tunnel underwent partial renovation in 2018, with drainage systems installed and potholes repaired, but it still requires substantial improvement, according to specialists.

Dangerous Roads stated: "The tunnel is dark and dangerous with hardly any lights inside, and it's suffocating as there's no ventilation but one fan."

"Locals have shared stories of a number of people dying inside it due to traffic jams that leave people trapped, where they succumbed to carbon monoxide. The poisonous air in the tunnel is barely shifted by one solitary fan somewhere in the middle of the tunnel, which gives some, but not sufficient, movement to the air.

"Expect huge, axle-snapping potholes threatening to swallow up the car, along with flooding that almost turns them into tunnel ponds. Your whole SUV can submerge if you drive in the wrong place.

"There are no road markings, so driving on the left or the right are optional, with the middle being the common choice.

"Halfway along the tunnel, water floods the road as a result of an engineering fault. Oncoming cars and trucks emerge in the darkness with headlights flashing for the other drivers to get out of their way."

One visitor detailed their experience on Tripadvisor, writing: "We went through this tunnel twice with no ill effects other than fear!"

"The traffic was two-way, and the darkness and lack of ventilation were scary, but we survived. The drive was scenic and fabulous and well worth the risk."