In just a few days, a well-known conference center and national landmark in Harriman will close its doors for good. Edward Henry Harriman built the Arden House 100 years ago. In 1950, through the efforts of Dwight D. Eisenhower, then president of Columbia University, it became America?s first conference center. In recent years, its main purpose was to host executive education programs run by the business school. As a result of a change in global business and education, the Arden House will close Monday and more than 100 employees will be laid off. University officials say there will be no mass development and whatever happens; the environmental and historical integrity of the house will be maintained.