Complex sentence: It was called the Waterloo Recreation Complex until May 2001, when the word "memorial" was added after the city closed the Waterloo Memorial Arena to honour the 69 Waterloo residents killed in the two world wars.
Split into simpler sentences: It was called the Waterloo Recreation Complex until May 2001, when the word "memorial" was added after the city closed the Waterloo Memorial Arena. The building honours the 69 Waterloo residents killed in the two world wars.