The Temple of the Heavy Buddha, on Setthathirath Road in the old quarter, takes its name from the 16th-century bronze Buddha image inside the sim — one of the largest in Vientiane. The original temple was destroyed in 1828 with the rest of the city; the current buildings date from the 19th and 20th centuries.
Wat Ong Teu is the headquarters of the Sangha (Buddhist clergy) for the whole country, so the monks here include the most senior in Laos. Early morning is the best time to visit: monks chant, novices study under the trees in the courtyard, and the place is busy with daily ritual rather than tourists.