We gave Philadelphia one last try. The third time was, for the most part, the charm.
We went to the Franklin Institute, which is a science museum:
They were doing a really excellent Lego art display that travels from city to city and happened to be in Philadelphia at the time:
In addition to Lego, we did see some actual science-y stuff, including a rock that is older than the sun:
Check out the video for loads of awesome Lego art: