Complex sentence: What is today known as the Swissôtel The Stamford in Singapore surpassed it in 1986 and the Renaissance Center's central tower remains the tallest all-hotel skyscraper in the Western Hemisphere.
Split into simpler sentences: What is today known as the Swissôtel The Stamford (1986) in Singapore had surpassed it. Since 1986, the Renaissance Center's central tower has remained the tallest all-hotel skyscraper in the Western Hemisphere.