I love visiting Science Museums in other countries. American science museums are fun, but a bit generic, whereas you never know what you'll find in China.
Xiamen's Science Museum (厦门科技馆) is actually fairly modern and quite a nice place to take the kids on a rainy day. It has lots of exhibits, so even though some don't translate well to non-Chinese speakers, there's plenty to occupy you.
There's the world's only eight-meter-tall water clock, the "real Tangshan earthquake experience" of a 7.8 magnitude earthquake, and a one million volt high-voltage stage performance, which sounds wonderfully dangerous. They even promise the mystifying "first three-dimensional dynamic 4D movie."
The museum is open from 09:00 to 18:00 and costs 80.00 yuan to enter.