LONDON, March 26 (Xinhua) -- One of the oldest secrets of Edinburgh's world famous castle was revealed Monday with 3D and laser technologies.

Historic Environment Scotland (HES), custodians of Scottish heritage, used technology to reveal precise details of one of the castle's most hidden structures, a well dating back at least 700 years.

The well, known as the Fore Well, was the primary source of water for the medieval castle, cut deep into the volcanic rock which towers over the Scottish capital city.

It first appeared in historic records in 1314, when it was deliberately blocked by Robert the Bruce's troops as part of wider destruction of the castle to prevent it being used against them, but the well is thought to be older. In its long history it provided a vital lifeline to the castle's residents throughout many sieges.

During the Lang Siege in 1573, it was completely blocked by falling masonry from the bombardment of David's Tower and rendered unusable. It was subsequently cleared in the following century and brought back into use.

The well was first surveyed in 1912 by William Thomas Oldrieve, Scotland's official architect. Oldrieve's detailed drawings of the well allow for comparison with the new 3D models demonstrating the accuracy of the hand measurements taken more than a century ago.

Rachel Pickering, HES Cultural Resources Advisor welcomed the laser scanning and the insight provided, saying: "Very little survives of the medieval castle and it can be hard to understand or appreciate how the early castle would have looked. Exploration such as this helps us to look at the castle in a new light and will continue to help us reconstruct and bring to life the lesser known aspects of the castle's past."

The castle is Scotland's most popular international paid-for tourist attraction.