In centuries past, traders would gather on this man-made plateau to haggle for goods from India and Tibet before starting the long trek to Lhasa or the Indian plains. It was also a former parade ground for Gurkha soldiers. These days it's a local picnic spot and viewpoint. On a clear day, a stunning panorama of Himalayan peaks is visible, including Dhaulagiri (8167m), Machhapuchhare (6997m), Langtang Lirung (7246m), Manaslu (8162m) and Ganesh Himal (7406m). Try sunrise or sunset.
Note that you can now get the same views with a hot coffee or beer at Bandipur Adventure Camp. This may be a better choice as locals can get rowdy at Tundikhel, particularly on weekends during the picnic season (October to November).