You can reach Dehradun by Flight from Kathmandu. By Train - Reach Raxual junction by bus from Kathmandu. Then by train to Laksar junction.. then to rishikesh
The distance is 740km, so by bus means long journey. It’s easy to reach Rishikesh from Delhi. Till Delhi there are direct buses. Then again from Delhi you might have to catch Rishikesh bus. You can check with MMT, Yatra and Goibibo for online bus services. There are sleeper buses too. Easiest way just sharing a suggestion, fly till Delhi then take a bus to Rishikesh. Upto you.
There is No Direct bus from Kathmandu Nepal to Rishikesh. But there are plenty of options by which you can reach Rishikesh from Kathmandu. 1) Flight - Take Direct flight from Kathmandu to Delhi . And then you can take Direct Train or bus from Delhi to Rishikesh. But it will cost you more. So I will not recommend this option to you. 2) Train - There is no direct train from Kathmandu to Rishikesh . You can reach to Raxaul Jn by bus and then take train from Raxaul Jn to Laksar Jn. Take another train or bus from Laksar Jn to Yog Nagari Rishikesh 3) Bus: There is no direct bus from Kathmandu to Rishikesh. You can take a direct bus from Kathmandu to Delhi . And then Delhi to Rishikesh
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