The Telephone STD code of Dehradun, a city in Uttaranchal is 0135. As such any telephone calls you receive with the Indian international code of +91 followed by (0) 135 will have originated from this city.
Similarly if you want to phone a company or organisation in this city you will need to use the telephone STD code 0135.
Dehradun is a beautiful city that is a popular destination for holidays among people living in Delhi. The valleys, rivers and surrounding views make it the perfect spot for a holiday.