HOUSTON-When it came to the office and retail markets during 2005, experts tell GlobeSt.com that, while investment activities were strong, leasing activities were even stronger, with news of Six Flags Astroworld's closing generating speculation as to its future, but no real surprise.On the retail investment side, "in 2004, we saw a feeding frenzy of buyers, with the low interest rates," says Shawn Ackerman, senior vice president with the Henry S. Miller Commercial's retail division in Houston. "This year, the sales transactions were strong, but the sellers were scarce."While sales transactions and investments might have been down, leases were strong both among office and retail properties. "It appears that managers and owners had a renewed confidence in the economy and were beginning to believe that their sales numbers were going to extend into the next couple of years," notes L. Ace Schlameus, vice president with Grubb & Ellis Co.'s Houston office.Schlameus adds that, during the second quarter of 2005, an increased number of inquiries came across the board, resulting in bona fide lease contracts. "Specifically, people in the retail markets in particular wanted to be fully established for the holiday sales season," he says.In addition, Ackerman says, the fourth quarter push for leases in 2005 was stronger than it was during the same period of 2004, "mostly from publicly traded retailers trying to hit their numbers," he explains.Robert Kramp also sees strong trends with retail leasing, because of expanding residential development. "It's not showing any signs of slowing down, either," adds Kramp, director of national client services and research with Grubb & Ellis' Houston office. An interesting real estate note was that the 109-acre Six Flags Astroworld, located near the Medical Center submarket, went on the sales block during late summer 2005. Sources at Cushman & Wakefield of Texas Inc.'s Houston office, which is representing Six Flags in its sales efforts, note that offers have come in for the property, but no closing has been announced.Still, "this is more emotional than financial," Ackerman says. "There isn't one person in the City of Houston in real estate that hasn't been there or taken their kids there. It's going to seriously change that whole real estate corridor that serves the Medical Center."Overall, experts agree that a strong 2005 will more than likely lead the way to a terrific 2006. Retail will continue to grow as residences continue to expand. Meanwhile, on the office side, notes Kramp, small deals will continue to push down already declining vacancies. "You can also expect vacancy to decrease further, due to a decline in the number of large, contiguous blocks of space in class A properties," he adds."Business and customers seem to be very optimistic," Schlameus concludes. "Existing tenants who have recently moved into smaller spaces are now seeking expansion opportunities within the same buildings."