Complex sentence: English Harbour is best known for Nelson's Dockyard, a former British Navy base; it displays restored 18th and 19th-century buildings and other historical artifacts from the colonial period of the dockyard, especially the time it was commanded by Horatio Nelson.
Split into simpler sentences: English Harbour is best known for Nelson's Dockyard, which occupies the site of the British Navy base. It displays restored buildings and other historical artifacts from the colonial period of the dockyard, especially the time it was commanded by Horatio Nelson.