Complex sentence: The cathedral is one of the most famous and most recognisable sights of London, with its dome, framed by the spires of Wren's City churches, dominating the skyline for 300 years.
Split into simpler sentences: The cathedral is one of the most famous and most recognisable sights in London. Its dome, framed by the spires of Wren's City churches, dominated the skyline for 300 years.