Find great value on Frontier Airlines flights from TUS to DEN when you book with CheapOair! If you are looking for fun, adventure and natural beauty, all in one place, then consider Denver. Surrounded by the beautiful Rocky Mountains, Denver would certainly impress you with the host of recreation opportunities offered. Whether you want to enjoy hiking trails in the Red Rocks Park or explore rare American paintings at the Denver Art Museum, the choice is yours. Kids are sure to have a great time at the Denver Zoo which is spread across an area of more than 80 acres and is home to more than 4,000 animals.