Located some 40 kilometres north west of Vientiane city, just 0.5 kilometres east of the main road from Vientiane to Luang Prabang, Ban Ilay Tai contains the remains of two ancient Buddhist sanctuaries, both probably of Mon origin. One comprises the remains of a sim surrounded by 10 bai sema (boundary stones), while the other features the base of a Buddha image perched on top of the remains of a sim, with remnants of a stupa close by. In May each year Ban Ilay Tai is still an important regional venue for the annual Boun Bangfai (Rocket Festival, see Traditional festivals), suggesting that it may once have been an important religious centre. To access the site visitors should turn eastwards off the main road just before the entrance to Wat Ilay and continue some 500 metres. The two sites are located 200 metres to the north and south respectively of a sharp bend in the road.