The Pleven Panorama is the city's signature sight: a purpose-built circular museum whose huge painted battle scene recreates the Siege of Pleven. It can sound old-fashioned, but the scale works, especially with a guide explaining how the siege shaped the Russo-Turkish War and Bulgaria's liberation.
The building stands in Skobelev Park, where much of the fighting took place. See it before wandering the surrounding memorial landscape; the geography makes more sense afterwards.