@pchopson thanks! It's a #visibilityGraph of a building using #SpaceSyntax. Shows how many 'visual turns' (looking around the corner) you need to see all spaces from a certain vantage point. Red to blue = short to long paths.
See here for a longer explanation including the actual example I've used (which is #Hogwarts castle - part of my #HarryPotter geekery).
https://spaceandorganisation.org/2016/09/21/teaching-and-learning-practices-at-hogwarts-the-role-of-the-school-building/