IMPHAL May 31: The Khangkhui cave, measuring an area of 5700 sq. meters located at Khangkhui Khullen in Ukhrul district has been declared as a Historical Monument and Archaeological sites in the interest of the public under sub- section (3) of section 4 of the Manipur Ancient and Historical Monuments and Archaeological sites & Remains Act 1976 said a notification signed by the commissioner (Art and Culture) Government of Manipur.