There is a dot for every land parcel in Massachusetts.

In a new map with about 2.5 million data points, Aaron Doucett, who brought you the MBTA walking map, has created a property value visualization of the entire state.

Doucett is a GIS analyst working in Cambridge who enjoys tackling big data sets to uncover geographic trends.

Each of the dots represents a land parcel, which you can choose to look at one of three metrics: total property value (as assessed by the town), cost-per-area (as in, price per square foot), or year built.

Purple and blue dots represent the most expensive homes (in the million-dollar range), green dots represent homes near state median value of $342,900, while red and orange dots represent homes below those values.

Doucett emphasizes that these property values are assessed values created by the town assessor to determine taxes on the property, as opposed to market values, which may be higher in many cases.

“In the examples on the map, I have tried to filter by just residential properties,” Doucett said. “As a result, some large apartment buildings and condos may not be included. The priority was 1-3 family homes, but depending on the level of detail provided by each town, some other types of residential properties have been included as well.”

Doucett notes that you can see distinct pricing zones emerge in certain areas, for example around I-495, Rt. 128, and Alewife Brook Parkway.

“It’s also very interesting to me how something like a town boundary can have a massive effect on property values as well, as can be seen looking at the border of Natick and Wellesley,” Doucett said.

Notice right at the Natick-Wellesley border the dots change from mostly blue to mostly green.

“I wanted to explore the spatial relationship of land values across the state,” Doucett said. “You can see how property prices skyrocket the closer you are to the heart of Boston. You can also observe how Cambridge, Brookline, and even parts of Somerville have become just as expensive as much of Boston.”

Play with the full interactive map on your own here.