Curaçao is mostly about beach- and nightlife, with plenty of sun, beach, watersports, bars and restaurants around. There are also two professional golf courses.
If you want to explore nature and culture, there are a few things to explore. The Christoffel National Park is a large park created in the 70s from three former plantations. You can drive through much of it (choose between the coastal route or the mountain drive), but you can also walk several short trails passing through stands of mahogany, limestone terraces and Amerindian petroglyphs. It is possible to climb to the top of Mt Christoffel.
Furthermore you can visit the colonial houses (“landhuisen”) of the old plantations. The Landhuis Savonet also has a museum on the island’s history and slavery.