Given the task definition and input, reply with output. Answer the question from the given passage. Your answer should be directly extracted from the passage, and it should be a single entity, name, or number, not a sentence.

Passage: There are also several smaller freight operators and numerous tourist railways operating over lines which were once parts of a state-owned system. Victorian lines mainly use the 1,600 mm (5 ft 3 in) broad gauge. However, the interstate trunk routes, as well as a number of branch lines in the west of the state have been converted to 1,435 mm (4 ft 8 1⁄2 in) standard gauge. Two tourist railways operate over 760 mm (2 ft 6 in) narrow gauge lines, which are the remnants of five formerly government-owned lines which were built in mountainous areas. Question: Where were the narrow gauge rail lines built in Victoria?
mountainous areas