One of our favorite runs in Singapore is to combine Gardens by the Bay with nearby Fort Canning Park, using paths along the Singapore River and Marina Bay to connect them.
Start with the ~2 km loop of Fort Canning Park — an iconic hilltop landmark once sited the palaces of 14th century Malay Kings and served as the Headquarters of the Far East Command Centre and British Army Barracks. This is one of the few places in Singapore to do some hills. There are expansive lawns and lush gardens, great for running, some good hills, stairs, and additional side paths. Fort Canning Park is located right at city center and reachable from most of the hotels.
Then, connect to Gardens By the Bay. It’s 2km on paths along the Singapore River, using the Esplanade & Helix pedestrian bridges. The Gardens is a top visited site in Singapore. Opened in 2012, it’s a spectacular 250-acre nature park, consisting of three waterfront gardens: Bay South Garden, Bay East Garden and Bay Central Garden. There are also numerous indoor gardens and conservatories (Flower Dome, Cloud Forest), for which ticketed admission is required. The best running — and where biking is also permitted — is the ~2.7 km along the waterfront promenade in Bay South and the perimeter of Bay East Interim Garden. One can add with the interior walkways of the outdoor trails, but they can be crowded at certain times and running might be discouraged.
Add-On: Marina Bay loop.