Spiti can be reached from two sides, from Manali via Rohtang La (3900 meters) and Kunzum La (4600 meters) and from Shimla along the Hindustan Tibet Highway that passes through Kinnaur. During the tourist season in the summers, visitors normally do a circular trip, i.e. enter via one side and exit via the other. However, in the winter, the Manali route gets closed due to snowfall in the high passes. One can still visit through the other route but it gets really difficult during the winters and only hardened adventurers venture into Spiti between December and March. BY AIR : The nearest major airport is Shimla and Bhuntar (Kullu-Malani), depending on which route you take. From there, you will have to get a bus or hire a car. BY TRAIN : The nearest major rail station is Kalka in the plains but you can also take the mountain railway (toy train) to Shimla and then again look for a bus/cab. If you are going via Manali, the nearest Major station would be Chandigarh. BY ROAD : You get buses from Manali as well as Shimla to Kaza. However, Shimla to Kaza is a very long way and it is better to halt somewhere in Kinnaur en route. SPITI ON HRTC BUSES : So, the most affordable way to explore Spiti is with HRTC buses. Buses are limited but they normally follow a reliable routine. You will also find local buses to many smaller villages from Kaza. I have made a separate post on bus timings as there are a lot of details.