Complex sentence: It was established in the 1900s, as part of the second wave of suburban development in Dunedin which came after settlers founded some of Dunedin's (and New Zealand's) oldest suburbs during the 1850s (including neighbour suburb Caversham).
Split into simpler sentences: It was established in the 1900s, as part of the second wave of suburban development in Dunedin. The first wave being the settlers who founded some of Dunedin's (and New Zealand's) oldest suburbs around 50 years before during the 1850s (most notably neighbouring suburb Caversham).