This is really cool, but why don't the color gradations go back further? Is it a matter of how records were kept? I would have loved to see how many buildings survive from each century from, say, 700AD on. Pre-1850 as a category seems like such a waste for a map of the old world.
Also, record keeping from that era isn't perfect - Reddit found that many old churches from ~ 1300 are labeled as 1600 or 1950, that being the date of the last extension or modification.
> Originating as a small fishing village in the late 12th century, Amsterdam became one of the most important ports in the world during the Dutch Golden Age, a result of its innovative developments in trade.
So I doubt there are a lot of buildings from 700AD left. But I agree, they could've gone back to ~1500AD.
The funny thing about the Netherlands, (or at least 90% of it) is that there is no natural stone to build with. No rocks, no pebbles, no stones, nothing. Just sand, clay and peat. In most places, the bedrock is hundreds of feet below the surface. Constructions were made of wood and mud, because everything else had to be imported.
In Amsterdam, most pre-17th century buildings were wooden, and didn't survive the fires. A cafe on Zeedijk (http://www.mokums.nl/aepjen.html) is one of the oldest buildings, dating from 1544. You know that it's really old because it's wooden (wood got banned as construction material after one of the fires).
That is very easy to answer: Other than churches and castles, pretty much all buildings up to the 17th century were made of wood, and did not survive. Only a few buildings predate 1800.
