About a half hours drive southeast of odessa tx, lies one of the biggest sand boxes in the state, Monahans Sandhills State Park. Thousands of years ago, high winds carried sand from the mountains of new Mexico and deposited along the southwestern edge of the high plains. Plants and vegetation have stabilized most of the sand dunes into the sand hills we know today. Active dunes continue to grow and change with the winds, with many of them reaching heights of over 40ft tall.  With no marked out trials, you are free to explore the dunes as you wish, just make sure to bring plenty of water in the hotter months. The park offers 26 campsite with both electricity and water, and the ranger station even rents sleds, to make the most of the dunes!