Vaishali in Bihar was one of the Buddha's favorite resorts and he visited it on several occasions. It was here that he had his famous encounter with the prostitute Ambapali, the incident is recounted in the Mahaparinibbana Sutta in The Long Discourses. Another discourse he delivered here is the long but interesting Mahasihanada Sutta from The Middle Length Discourses.
According to the Mahayana tradition the famous Vimalakirtinedesa Sutra was preached here too. About a hundred years after the Buddha's Parinirvana the Vaishali city was the venue for the Second Council where hundreds of monks from all over northern India met together to settle a dispute about Vinaya rules and to chant the suttas together.
The main things to see today are the famous lion pillar, the museum, the large Kharauna Lake, the Japanese temple and the stupa built over the Vijjians' one eighth share of the Buddha's ashes.