Exploring the whole city by yourself via train. Every main destination in this city can be accessed via train while you spent only around 2 USD per destination stop. They have a map nearby or you can download one via your App. different colors stand for different destination.
Merlion Park and the view from it! Sometimes it can get crowded, but still enjoyable. There are restaurants and Cafés right there in the area for convenience and rest a little to continue your detour. There's a boat ride available to explore around, and inform you about historical facts.