Johor Bahru is the state capital of the state of Johor and the second largest metropolitan area in Malaysia. Most tourists don't stop here and just pass through the city on their way to or out of Singapore. JB is a major local transportation hub however. Since it is just across the causeway from Singapore, some travellers use it as a hub to visit Singapore from here (lower accommodation prices) or to board the train, bus or airplane.
The Gunung Mulu National Park in Borneo (near Miri) is a UNESCO World Heritage Site with caves and karst formations. The caves are home to over 5 million bats who exit the caves in search for food every evening in a spectacular way.