There are two very famous Siddhapeeth Devi temples in Haridwar ? Mansa devi Temple at the top of the Bilwa mountain and Chandi Devi Temple atop the Neel Mountain. Both of these are dedicated to different forms of Goddess Shakti (a form of Goddess Durga) and offer excellent views of the town as well as the valley.
A convenient way to reach them is through the Udan Khatola or cable cars for which you will have to pay a nominal amount of charge. Tickets are available at the base of the hill. Round trip tickets are cheaper than the single round fare. If you are planning to visit both the temples, then combo tickets are also available at the counters. However, alternatively one can even decide to walk all the way to the temples (approx 1-1.5 km trek distance).