When I began planning a trip to Alaska, two words came to mind. One was “big,” which many things there are. The other was “mystique,” a sense which pervades the image that people often have of that state. It’s the size of the “Great Land,” as the Aleutian people named the region, which makes the most immediate, and dramatic, impression. Alaska is twice as large as Texas and if cut in half, would be the first and second biggest states in the country.   Mount McKinley is the tallest peak in North America, and Denali National Park over which it looms is larger than Massachusetts.