Tai Po Kau Nature Reserve.
Tai Po Kau Nature Reserve is a protected area just south of Tai Po town. It is covered by a lush forest, home to numerous species of animals. This includes mammals like the barking deer and civet cats, various smaller mammals, birds, frogs and many species of butterfly and other insects and bugs.
Fireflies
Late spring, most notably in May and June, many fireflies can be seen there. This includes actual flies, and various worms and other insects that emit light. Throughout the firefly season, different species become active. These fireflies are of course only active at night, main activity starts about an hour after sunset, when it's getting really dark. Then all over the forest little lights can be seen.
The best way to enjoy the fireflies is to set off around dusk or a little later. Bring a torch covered with red transparent film (or the tail light of your bicycle) so you can see where to put down your feet without blinding yourself. An bright white torch will allow you to see the path, but nothing else. Do have a bright torch at hand to have a better look at the bugs you find.
Outside the firefly season this area is of course still very much worth a visit, both during the day or at night.
And do remember to bring mosquito repellent. There are lots of bugs there of course. And especially at night they'll be craving for a meal.
The cache
The cache is hidden along the Tai Po Kau Nature Trail, near the junction with another path and a little bridge. You can start off at the car park (PARKNG) which is right next to the bus stop, and walk up from there.
Getting there.
Take KMB bus 72, 72A, 73A, 74A or green minibus 28K. Get off at Tsung Tsai Yuen bus stop, and walk 50-100m west to the entrance to the nature reserve. Minibus 28K may be boarded at Fo Tan MTR or Tai Po Market MTR station, ask the driver for section fare when boarding in Tai Po Market.