Tweed Heads is as far north as you can get in NSW, with the town abutting the Queensland border, and turning into Coolangatta on the other side, with both known as the Twin Towns. Whilst the area is a hotbed of activity, with tourism, shopping, surfing and some of the fastest residential growth in the state, this activity is nothing compared to the fireworks of some 20 million years ago, when volcanic action resulted in the largest caldera (volcanic rim) in the southern hemisphere.