Coming from the north you will have to travel through the Loetschberg. On 15th June there was the inauguration of the new railway tunnel which cuts down travel time significantly. The tunnel is the third longest in the world with 34.6 km length. It starts in Frutigen at 776.5 meters above sea level and goes up to 828.2 meters and leaves the mountain in Raron at 654.2 meters. Trains can reach a top speed of 250 km/h.
If you are not in a hurry to travel, you can still use regional trains after 9th December 2007 when the tunnel will be used for passenger trains. The old lines is way more scenic as you will see some mountains and travel through shorter tunnels and the trains climbs up much higher.
Favorite thing: There are lots of restaurants in Visp old town. When you come here, make sure you taste some local cheese dish and local wine. Wallis/Valais is a famous wine growing area in Switzerland.