Opened to the public by two pedestrian roads, this nature reserve is perfect for escaping the city. There's a wide variety of flora and fauna (birdwatchers will love the bird hides), and a variety of habitats, from mangroves to grasslands. Enter via the west entrance about 500m from Punggol Settlement; while here, use the bathrooms (there's only one on the island's east side) and stock up on water. You can also hire a bike (from S$8 per hour) here.
Come early to spot lots of animals; a family of otters loves to bask on the beaches here. Besides all the lush vegetation, there is also an abandoned mansion – built by the famous Haw Par brothers of Tiger Balm fame – but it is located in the mangroves, so if you'd like to see it, you must join one of the free guided tours offered by the National Parks Board; check the website for details.