Complex sentence: The present stadium is an extended version of the original Gateshead Youth Stadium, which was built in 1955 at a cost of £30,000 and which has been heavily renovated since, most notably in the early 1970s and again in 2006 and 2010.
Split into simpler sentences: The present stadium is an extended version of the original Gateshead Youth Stadium which was built in 1955 at a cost of £30,000. The Youth stadium has been heavily renovated since it opened, most notably in the early 1970s and again in 2006 and 2010.