Underground tunnels are among the most remarkable engineering achievements in human history. These structures, which have revolutionized many areas such as transportation, water conveyance, security, and urban infrastructure, have been seen as gateways to the mysterious depths beneath the earth. Tunnels, which have been dug in various regions throughout history for different purposes, have sometimes been a necessity for survival and sometimes a sign of technological advancement. The first of these tunnels, from the perspective of modern engineering, is considered to be the Thames Tunnel, built in the 19th century in England.
However, humanity’s interest in the underground is not limited to the modern era. Since ancient times, people have constructed underground structures for water channels, mining galleries, and shelters. Examples such as the Terelek Rock Tunnel in Turkey prove the existence of tunnel architecture dating back thousands of years. Today, massive underground tunnels are being built using advanced engineering techniques, both to facilitate urban transportation and to establish connections between countries. In this article, we will seek answers to the most curious questions about which country built the world’s first underground tunnel.
🌍 In Which Country Was the First Underground Tunnel Built?
The first modern underground tunnel was built in England. This tunnel is known as the Thames Tunnel and was constructed to pass beneath the River Thames. Construction began in 1825, and the tunnel was completed and opened for service in 1843. The Thames Tunnel is not only the first tunnel in the world to pass under a river but is also considered the beginning of modern tunneling history.
However, underground tunnels were also built in earlier periods in different regions. For example, the Terelek Rock Tunnel in Turkey, which dates back approximately 2,000 years, is a significant underground structure from ancient times. So, from a historical context, underground tunnels built with different technologies in various periods do exist; but according to engineering history, the first modern underground tunnel is the Thames Tunnel in England.
🏛️ When and Why Was the Thames Tunnel Built?
The construction of the Thames Tunnel began in 1825 and was completed in 1843 after long and challenging work. This tunnel went down in history as the first underground passage to run beneath the River Thames in London. Built despite major engineering difficulties using the advanced technology of its time, the tunnel was designed by British engineer Marc Isambard Brunel and his son Isambard Kingdom Brunel. During the construction, a special technique called the “tunnel shield” was used for the first time, which later became widely adopted in tunnel construction around the world.
The purpose of building the Thames Tunnel was to ease river traffic and establish a direct connection between South London, enabling the passage of pedestrians and horse-drawn carriages. The growing commercial and transportation needs of the time made such a structure necessary. However, due to financial problems and structural difficulties, the tunnel was initially used only for pedestrian passage. In later years, it was converted into a railway line and began to play an important role in transportation infrastructure. The Thames Tunnel became a groundbreaking structure in the engineering world with both its technical success and its role in transportation history.
🏗️ What Are the Features of the Thames Tunnel?
The Thames Tunnel is approximately 396 meters long, 11 meters wide, and 6 meters high. This tunnel, which passes beneath the River Thames, was built to connect both banks. The most notable feature of the tunnel is the use of a special excavation technique called the “tunnel shield” for the first time in its construction. This method reduced the risk of collapse in the excavation area, ensured the workers could operate safely, and laid the foundation for modern tunneling techniques. With this feature, the Thames Tunnel marked a revolutionary step in the history of global engineering.
Originally planned for pedestrians and horse-drawn carriages, the tunnel was converted into a railway line toward the end of the 19th century. Today, it is still in use as part of the London Overground line. During its time, the tunnel became a major tourist attraction, housing shops, concert venues, and entertainment spaces. Although it lost these functions over time due to structural deterioration, the Thames Tunnel still serves as an active transportation route today and retains its historical significance as the world’s first modern underground tunnel.
🏺 Where Was the Oldest Tunnel in History Found?
One of the oldest tunnels in history is considered to be the Terelek Rock Tunnel, located in the Central Anatolia region of Turkey, near the province of Kayseri. This tunnel was built around 2,000 years ago during the Roman Empire. It was constructed primarily to redirect the water of the Kızılırmak River and served a practical purpose such as irrigating agricultural lands in the region. Carved into the rock, this tunnel is regarded as a major engineering achievement considering the technical means of the time.
The Terelek Rock Tunnel is significant not only for its functionality but also for demonstrating the advancement of ancient engineering knowledge. The carving and drainage techniques used in its construction later inspired water tunnel and canal projects in subsequent periods. Still standing today, this structure is one of the rare examples reflecting the rich history of underground architecture in the Anatolian region. The Terelek Rock Tunnel is recognized as one of the first underground tunnels in history and shows how early humanity began engaging in underground engineering.
🚇 What Is the First Underground Rail System in Turkey?
The first underground rail system in Turkey is the Karaköy-Beyoğlu Tunnel located in Istanbul. Opened on January 17, 1875, this tunnel is considered the second oldest metro in the world. It was built for passengers who had difficulty climbing the steep slope between Karaköy and Beyoğlu (known at the time as Pera), and it operates using a funicular system over a length of approximately 573 meters.
The purpose of constructing the Karaköy-Beyoğlu Tunnel was to ensure that merchants and travelers arriving at the Galata Port during the Ottoman period could easily reach the hotels and commercial centers in Pera. Designed by French engineer Eugène-Henri Gavand, the tunnel both facilitated transportation and marked a turning point in urban transit in Istanbul. Still in active use today, this system is the first underground rail transport structure in Turkey and maintains its place in Istanbul’s transportation history.
🧭 What Are the Features of the Karaköy-Beyoğlu Tunnel?
The Karaköy-Beyoğlu Tunnel is one of Istanbul’s landmark structures, being Turkey’s first underground rail system and the second oldest metro in the world. Measuring 573 meters in length, 6.60 meters in width, and having an elevation difference of approximately 60 meters, this tunnel enables passengers to overcome the steep slope between Karaköy and Beyoğlu in about 1.5 minutes. A funicular system (a carriage pulled by cable) is used, indicating that the tunnel was designed in accordance with its sloped structure. Two carriages move along a single rail line between both ends.
When first opened, the tunnel served horse-drawn carriages and passengers. It was later modernized by switching to steam-powered and then electric systems. Today, the tunnel operates as part of the Metro Istanbul network and carries approximately 20,000 to 25,000 passengers daily. Despite its short distance, the Karaköy-Beyoğlu Tunnel holds great historical and technical significance, facilitating transportation while continuing to stand as an important structure that reflects Istanbul’s urban heritage.
🔍 What Are the Other Important Underground Tunnels?
Here are some of the other important underground tunnels in the world:
- Channel Tunnel (Chunnel) – Connecting England and France under the sea, this 50.5 km long tunnel is one of the longest underwater tunnels in the world.
- Gotthard Base Tunnel (Switzerland) – With a length of 57 kilometers, it is the longest railway tunnel in the world. It runs beneath the Alps and was opened in 2016.
- Seikan Tunnel (Japan) – Connecting the islands of Honshu and Hokkaido, this 53.8 km long tunnel is the second longest underwater tunnel in the world.
- Qingdao Jiaozhou Bay Tunnel (China) – This road tunnel, approximately 7.8 km long, runs under Jiaozhou Bay and is one of Asia’s important underwater tunnels.
- Tokyo Bay Aqua-Line (Japan) – A bridge-tunnel hybrid structure running under Tokyo Bay, with the tunnel portion being about 9.6 km long.
- Laerdal Tunnel (Norway) – At 24.5 km in length, it is the longest road tunnel in the world. It was built to ease transportation in Norway’s challenging mountainous terrain.
- Delaware Aqueduct (USA) – This tunnel, approximately 137 km long, is the world’s longest underground water tunnel, supplying water to New York City.
- SMART Tunnel (Malaysia) – A multifunctional tunnel used for both traffic transit and floodwater drainage. It is located in Kuala Lumpur.
- Brooklyn-Battery Tunnel (USA) – A historic tunnel in New York connecting Manhattan and Brooklyn.
- Marmaray Tunnel (Turkey) – A 13.6 km long railway tunnel in Istanbul that connects the European and Asian continents under the sea. It was opened in 2013.