The Sensex at the Bombay Stock Exchange soared 485 points, the biggest single day gain in the last six months.It touched a fresh 33-month high of 20,688, today, amid rising global markets, and expectations that the US central bank will provide further stimulus measures. The Nifty at the National Stock Exchange climbed 143 points to 6,234.Stock markets in Japan, China, Hong Kong, Singapore and South Korea rose between 0.2 percent and 1.7 percent.