Nerva was 66 years old when Domitian was assassinated and was considered a safe choice for temporary emperor since he probably wouldn't live long. During his reign, a good successor could be chosen. He completed a new forum which Domitian had started, and named it the Forum of Nerva when it was dedicated. He died of natural causes less than 2 years after becoming emperor.
Nerva, in the National Museum of Rome - Palazzo Massimo See all Nerva photos.