When one was only 1.5 years old, she mostly just stayed in a carrier on my wife's back while she explored the area, going on day trips and running errands like buying groceries (which in a foreign country can be fun on its own). When we had a 1 year old and a 3 year old, we were nomadic for about 2 months and we mostly found an airbnb for a week-month and drove on the weekends. During the day, the kids and wife would go to local playgrounds, public libraries, state parks, national parks, beaches and kids museums (a membership at one gets you a membership at most in the US).

Now that our oldest is about start kindergarten, we're more interested in staying in one place so she can make longer lasting friends, but when they were younger it was a lot of fun. The sweet spot for us was when they were too young to walk and could ride in the carrier for hours on end, or old enough to walk well and be interested in more activities and places. In between was harder: not wanting to be carried, but not really capable of walking for more than a few hundred feet at a time.