Huangyaguan was originally built over 1400 years ago in the Northern Qi dynasty and reinforced with brick walls during the Ming dynasty.[1] In 1984, major repair work was performed on over 3 kilometres of the wall including on 20 water towers and 1 water pass.[2] The pass is a major tourist attraction within Tianjin and was listed as a site of relics protection in 1986. Recently found drawings on the walls showed the builders of the wall smoked cones for every metre of the wall they completed.[citation needed]
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