Salem is a large industrial city in north-central Tamil Nadu, surrounded on three sides by hills. It's a significant steel production centre and a busy transport hub, but most travellers pass through it rather than stopping here.
The main reason to stop is Yercaud, a hill station 30 km northeast at 1,600 metres altitude in the Shevaroy Hills. The road up offers good views and the top has a lake, botanical garden, and the relative cool of the Ghats. It's less visited than Ooty or Kodaikanal and correspondingly less developed — which is either a drawback or a selling point depending on your preferences. Kiliyur Falls, a few kilometres from the town, drops 300 metres and is worth the short walk.
Salem itself has a fort (the oldest building in town, though not much is left) and a reasonable museum. The Sugavaneswarar Temple is the main religious site in town.