Hours of gazing
(Recommended)
Pros
If you went to school in the London area, you went on a school trip to the Science museum.
If you didn't, get down there now. There's loads of stuff to see in here, your day will disappear really quickly. There's space stuff, boats, cool gadgets, old cars, planes, engines, computers and a big ring in the middle of the place that asks you questions about the environment. When you put in your answer it shows up on the ring... Now it used to show up straight away but they changed that. I like to think some of things I used to put on the large lcd display contributed to this.
Definitely check out the electrocution pole-thing. Have you got the guts?
There's also an IMAX cinema in the science museum that's well worth the look. If you've never seen a 3D film, you don't know what you're missing. I was always wowed by these things. The sea show is very good, marvel as squid fly above you head... That stuff doesn't happen every day...
The science museum shop is great fun... Potato powered alarm clock... score.
Cons
None given.