This is Jantar Mantar, an astronomical observatory in Jaipur, India completed in 1734. It contains this machine, the world’s largest stone sundial. The king Jai Singh built dice observatories across India to calculate the position of the heavenly bodies, all without the use of telescopes.
As the article correctly states it is the largest STONE sundial. The largest sundial of the world is made out of steel and is located in Zaragoza (Spain). It is also the most accurate. It holds the Guinness record.