Patuxai

Also called Patuxai Arch or the Arc de Triomphe of Vientiane, it is a local rendition of Paris' Arc de Triomphe with typically Laotian in design, decorated with mythological creatures such as the Kinnari.
Besides the elaborate Buddhist embellishment, it differs from the original in having four gates instead of two and being just a bit higher. A surprisingly frank English sign inside the monument labels it a "monster of concrete" when seen up close. The monument itself aside, the palm tree-lined park around it complete with fountains is quite pleasant though lacking of shade during the day time. 
You can climb up to the 7th story for a nice view of central Vientiane and three levels of souvenir shops with less than enthusiastic sales people sitting about. A musical fountain nearby attracts visitors from around Laos and Asia, and a World Peace gong is presented by Indonesia. Roving cameramen will be happy to charge you for photos near these attractions.