The Co Loa Citadel just north of Hanoi is claimed to be the oldest fortification structure build in the Red River delta, with finds from the site dating to the Dong Son period.
Co Loa Citadel, Viet Nam Net 20141206
Co Loa offers glimpse into past
Viet Nam Net, 06 December 2014
The site of an ancient Vietnamese citadel has been suggested for inclusion into the World Heritage register. The Co Loa Citadel situated north of Hanoi was established around 200 BCE, and a number of Bronze Dong Son objects have also been found there.
Co Loa Citadel, Vietnam Net Bridge 20110407
Co Loa ancient citadel proposed as world cultural heritage
Vietnam Net Bridge, 07 April 2011
A feature on the numerous ancient citadels around Hanoi.
Hanoi boasts many ancient citadels
VOV News, 24 September 2010
The Culture, Sports and Tourism Minister of Vietnam has highlighted the need for new legislation to meet the demands of heritage conservation work, especially in the light that many conservation projects do not meet quality standards and have even led to the damaging of some of the relics.
Legislation to save nation’s heritage [Link no longer active]
Viet Nam News, 13 April 2009