This is Maison Careé, Nîmes, one of the best preserved Roman temples in the world. 

It was built in approximately 16 BC, and owes it’s preservation to the fact that it was rededicated as a Christian church in the fourth century. Although it’s been through a good number of other uses - including a stable for the government’s horses during the French revolution - since 1823 it has been a museum. 

It’s original dedication was to Gaius and Lucius Caesar, adopted sons of Augustus Caesar who died young, by Marcus Vipsanius Agrippa, the close confidant and general of Augustus who was hugely responsible for his success.