When digging was completed in 1888, The Big Well became, and remains (at 109 feet deep and 32 feet in diameter) the world's largest hand dug well. Created to provide a reliable source of water for both the city of Greensburg and the railroads, the well remained in operation until 1932 and was opened as a historic attraction five years later. Today's museum divides its attention between the Big Well itself and the 2007 EF5 tornado that destroyed 95% of Greensburg. Today, the city has been rebuilt, reinventing itself as a sustainable, model green community.
If you go:
The new museum was completed and opened in 2012 and it's possible to descend into the Big Well or climb to the observation area at the top, via a spiral staircase. Opening hours are 9am-6pm Monday to Saturday; 1pm-6pm Sunday.
Links:

The Big Well Museum & Visitors Center
315 S. Sycamore
Greensburg, Kansas 67054 USA
Phone Numbers:
+1 (620) 723-4102