The Knights Templar were, and remain, one of the most potent and prominent orders in the history of humanity. For over two centuries, they were involved in military, commerce, and politics in different countries in Europe. Even after their fall in the 13th century, they left an irreversible impact on the way Christian orders are perceived in the world. It is even possible that today in the 21st century, there are people who follow the steps of the Knights Templar. Originally, the order started to aid Christian pilgrims who traveled from Europe to the Middle East to visit and also trade. Their first home was in the Temple Mount, which inspired their name, as they portrayed themselves as the guardians and protectors of the Temple. After Saladin conquered Jerusalem, they settled in the Old City of Acre instead, where they built their headquarters. Their fortress was one of the strongest in the area. On the entrance, you'll find two thick towers, in addition to two small tunnels on each side.
Under the city, they built a tunnel that runs from their site in the southwestern section to the southeastern section, where there is a sea. The tunnel was 350m long, and it was built as a secret passage that connects their site to the port. It works both, a good way to transfer goods and also as an escape in case of an emergency.
The tunnel was not discovered until 1994 accidentally by a plumber when it was flooded with water. In 1999 the Antiquities Authority of Israel opened the eastern section of the tunnel to the public. Since then, they worked on rehabilitating the western section, which itself was made available for visitors in 2007.
The tunnel of the Templars was not discovered until centuries after their last trial. With so much being revealed about the order, there is a lot still unrevealed.