Zillow heat-maps Valley land prices

The Zillow real estate site won me over from day one by mapping house prices for every zip code and address (even if it grossly underpriced the Japanese villa of Oracle's Larry Ellison). So when the developers made a heat map of San Francisco real estate rates, I asked them to stretch that map across the whole Valley. They answered with the giant map here — stretch the window to enlarge it, or view it full-size.

Check out the peninsula — what should we call that band of red streaking across Atherton? And the deep purple pool of San Jose proves what we all knew: No one really wants to be in San Jose.

Cool data on what's hot [Zillow blog]
Update after the jump.

UPDATE: Amy Bohutinsky at Zillow says:

Fyi — Ellison's Japanese-style home is the one in Atherton. Currently listed for $16M (recently lowered from $25M). http://www.apr.com/DesktopDefault...

Zestimate is $17.9M:
http://www.zillow.com/search/Search....

But... In general we are always going to be less accurate at first glance for homes on the extreme high end. Couple of reasons for that:
1) Our Zestimate algorithm looks at recent sales of comparable homes to estimate what a home may be worth today. When you get that high, we're going to have many fewer homes to compare with.
2) Most homeowners like Larry probably have done some extensive renovations or additions since the last sale that we may not know about. So he would have to use the "My Zestimator" tool to factor these in for a more accurate value.