The London Underground diagram

Beck threw away geography: straight lines, forty-five degree angles, even spacing between stops. What a passenger needs is the order of stations and where to change, and almost every metro map since has agreed.

Preview from Wikimedia Commons, public domain, shown from their site.

By
Harry Beck · 1933
Where
Data art · Transport
Form
Static image · to inform
Visual
Connection, Colour, Position

The chart types behind it