We usually call it outward bound training. You can find a local company specializing in outreach activities to help you plan, and then show the quotation and plan to your boss.

If you organize yourself, you can contact local attractions, manors and so on. They generally have experience in hosting such activities. Then you tell them how many days they need to do activities, one or two days a week, and then pick up, stay and exercise, but it's troublesome and tiring.

If the boss just wants simple activities, then rent a sports venue. Anyway, larger space is enough. Prepare some prize drinks, banners and slogans, set up some fun sports for the activities, organize cheerleading, and make it lively anyway.