Nguom Slua is a cave developed in a limestone massif, which in turn was formed under shallow and warm marine conditions c.270-360 million years ago (Carboniferous-Permian periods). Near the cave entrance are remnants of two river terraces that are evidence of recent (so-called Neotectonic) uplift of the area. According to legend of the Tay people, Nguom Boc cave was the place for meetings and engagement of the couple Pu Luong and Slao Cai, whereas Nguom Slua was where Pu Luong fought back the tiger to protect his family. Nguom Slua was the place where the Co Do (Red Flag) Newspaper was printed during 1932-1933, and was also the revolution base from 1932 to 1936. It was also at this place that the Cao Bang Party Committee held the Indochina Congress in May 1936 to call for the support of the “Indochina Congress” movement from different ethnic groups within the province. The "Petitions" were also drafted here to request democratic reform, improvement of people’s lives and legal public opposition. Nguom Slua was recognized as National Historical Monument pursuant to Decision No. 188/VH/QD/BT dated February 13th 1995. View more