Kalgoorlie-Boulder was founded on gold.. it continues on gold. 600km from Perth, it's not exactly a day trip. Easily accessibly by plane or train, or for the adventurous.. a seriously boring drive.
Kal is home to an amazing engineering feat in the pipeline; a water pipe that feeds the Goldfields from Perth. And is also the hub for the rest of the Goldfields. In Kal itself, you can look at the Superpit (ie: a giant hole in the ground), other mining related activities, try your hand at a bit of prospecting, drink a beer whilst being served by skimpies, or just wander down Hay St - the red light district, where you can actually take a tour of one of the establishments and enjoy a coffee at the "Miner 69er Cafe".
As bad as I make it sound... Kal is an experience that most tourists enjoy :)