Complex sentence: Most of the city centre was rebuilt in the years following the war, but as recently as 2006 researchers found documents in the local archives that suggested an unexploded wartime bomb might be buried beneath a major new redevelopment, The Boom, in Hull.
Split into simpler sentences: Most of the city centre was rebuilt in the years following the war. As recently as 2006 researchers found documents in the local archives that suggested an unexploded wartime bomb might be buried beneath a major new redevelopment, The Boom, in Hull.