Complex sentence: Today, the largest concentration of hotels in Fiji has grown up in and around Nadi, and as tourism took off in the 1960s, the nearby resorts under construction in the nearby Mamanuca Islands and Denarau Island cemented Nadi as the centre of Fiji's tourism industry.
Split into simpler sentences: Today, the largest concentration of hotels in Fiji has grown up in and around Nadi. As tourism took off in the 1960s, the resorts under construction in the nearby Mamanuca Islands and Denarau Island cemented Nadi as the centre of Fiji's tourism industry.