This slender, crammed hole-in-the-wall place directly east of Hoan Kien Lake has narrow tables and stools where it's all elbows and chatter. The place has been going since 1955, serving steaming bowls of beef noodle pho in three sizes (small, big and jumbo); extra beef costs from 30,000d and a poached egg thrown in is 5000d.
Vegetarians can just ask for egg; add chilli according to taste.