Dehradun is a base for trekking and adventure tourism, and many people just stay overnight in the city before heading into the Garhwal Hills.
Pack a hamper of food and drinks and picnic at sahastradhara, on the banks of the baldi river. the mineral waters here are pure and clean. it is a 30 minute drive from the city of dehradun. you can also rent a cycle from hotel madhuban. it takes a little over an hour to bike down.
After a hard day's sightseeing, drive down to the village of Dakpathar 45 km away. The sparkling waters of the Yamuna makes this the perfect spot to relax. The neat little GMVN Tourist Complex is located inside the village. It has a good restaurant and a small swimming pool.