During the seventeenth and eighteenth centuries, the entire site became covered with a layer of hard grey clay, which minimised further erosion.
在十七世纪和十八世纪，整个遗址被一层坚硬的灰色粘土覆盖，这极大减少了进一步的侵蚀。
2
Everyone at the site worked hard to finish building the tunnel on time and more than 10 latest techniques were developed while the workers were doing this great project.