It depends on what level of training you require right now. For marathon: - Trail : Bukit Timah, Pulau Ubin - SD (Short Distance) - LD : East Coast Park - Changi, the return is about 40km - SD in the CBD: along the river is very nice For Bike: - SD: Again ECP-Changi, Mandai Rd - LD: Desaru and Mersi...