The Archaeological Museum of Sarnath is quite a simple museum but it boast of being South-Asia most famous of its kind. It has a lot of artefacts, edifices comprising numerous Buddha and Bodhisattva images, other ancient remains and sculptures depicts the vibrant religious activity that has surrounded Sarnath for more than a thousand years.
It is also next to some very interesting historical ruins.
Be advised that they do not allow you to take bags cameras or mobile phones inside the complex (which was very daunting even though it was guarded), so they provide lockers to leave your valuable.