According to the ParisDailyPhoto, a cool blog with lots of photos of Paris annotated in English, you must get yourself to the top of the big arch of La Défense.
This place is like heaven for geeks, believe me. Not only can you see what a computer looked like in the 40’s (well, OK, maybe they did not really qualify as computers…) but also discover – or rediscover, depending on your age – the first PC, the first laptop, the first Apple Macintosh…
Read: A Must See Museum