The most visible and historically significant of the battlefield sites accessible from the town centre. Hill A1 — the Viet Minh designation; the French called it Élianne 2 — was the key high ground commanding the central French position, and the fighting for it was among the most brutal of the entire siege.
The hill is now a park and memorial site. At the top, a crater marks the site of the Viet Minh mine explosion of May 6–7, 1954. A bunker entrance is preserved and can be entered (bring a torch). The view from the summit across the valley floor — where French defensive positions once stretched — is worth climbing for in its own right. Vietnamese families picnic here at weekends, giving the site a quietly domestic atmosphere at odds with its history.