Situated just "past" (on the coastal side) of Jiufen, you can get here by bus or car. If you drive, you can park in the No. 1 carpark, which right by the entrance, or drive over to the No. 2 entrance, and enjoy a beautiful paved and flat scenic walk behind the temple to the entrance. (DO NOT pay $100 to park your car and then walk up the steep slope to the museum, like I almost did!) On the way, you can go to the WWII POW building, where British soldiers were kept and made to work in the goldmine, the POW memorial, or even walk up Teapot Mountain.
This year (2010), entrance to the park is free, but the entrance is really reasonable (150 per adult) should you have to pay. For 50TWD you can go into the remodelled Shaft No. 2, and I highly recommend that walk. With recordings, simulations of mine workers, and very safe walkway construction, it's a worthwhile experience for even little kids.
There is a beautiful Japanese building that was built for a Japanese prince who was supposed to visit during WWII, Japanese gardens, nice little gift shop, simple restaurants and a cafe.
My children (ages six and four) loved this entire adventure. We spent about four hours exploring the park, and then drove down to the coast before returning to Taipei. Next time I have overseas guests, I will skip Jiufen and take them to this park.
The English (and Japanese) website is comprehensive.
Hours: Tues-Fri 9:30am-5pm; Sat/Sun 9:30am-6pm
Map and Address: http://www.gep-en.tpc.gov.tw/econtent/travel/travel.asp