Maps are all very well and good – but seeing an actual photograph of a city from above, especially at night, is way cooler. You can see where lights, and human activity, cluster; you can see, effectively, what an astronaut sees when he looks down.
The image above shows London from space, as taken from the International Space Station on 2 February, 2013. The first things you notice are the oddly comforting boundary of the M25 circling everything (though it goes a bit dark to the southeast) and the Thames, jaggedly bisecting the centre. The black, lightless patches represent parks: Kensington Gardens, Hyde Park and Regent's Park are the most obvious.
Look a bit closer, though, and a few other things start to stick out. First, colour: most of the lights are a pale yellow, building to a white roar in the busiest spots.
But there are also occasional blips of other colours, mostly red, purple and green. In general, these mark out large monuments or buildings, colourfully lit up to attract attention.
The image below shows the section of the river around waterloo, and the circled, colourful section covers the London Eye, Southbank Centre and the IMAX cinema, all of which are often colourfully lit up at night:
In terms of brightness, the hotspots are in Soho (visible at the top of the photo above), and also an oddly shaped area to the West:
Okay, obviously, it's Heathrow. As you can imagine, it's pretty helpful for an airport to have a distinctive shape from above – especially if it's so busy it forces many flights to circle above the city for hours before landing.
Here's a close-up, courtesy of the Canadian astronaut, Chris Hadfield. Just to confuse you, this one's upside down:
Click to expand.
And here's one last picture, of London from above during the day:
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The grey areas are built up; the blue is obviously water. The heavily industrialised areas – the Thames, Lea and Wandle valleys, as well as Heathrow and Old Oak Common – are, unexpectedly, shown in white. So, at first glance, are some of the fields of Essex and Kent – a measure of what industrial-scale agriculture can do to a landscape.
Nonetheless, the overwhelming impression you're left with is of quite how green London is. Just look at all that lovely empty space.
All images placed in the public domain by NASA.