Give them a super good river
You're a benevolent God, so give your people a nice, reliable, tamable river. I'm not sure what is irrigating your farmlands, but I'm going to argue that a river naturally will get people to move and explore.
A river will make people want to spread out, gradually extending out the civilization and causing them to build towns and hamlets farther and farther away from the main city. Here's some reasons why:
Fish
Fish are a great source of protein. Fish guts are a great source of nitrates which can improve crop yields or reduce the amount of time a field must lie fallow between usages. Fishers would gradually spread out over the length of the river to try to find different pockets of fish or just to go upstream of a popular spot that is being overfished.
Farmland
A good river deposits nutrient-rich silt and irrigates the landscape, meaning that all up and down its banks would be super fertile, especially compared to the surrounding landscape. Nearby animals would come and graze on the grass growing near the river, as well as drink there, meaning the river banks would become great spots for hunting, too. Any enterprising farmer would want to settle away from the rest of the other farms to try to get more good land to till.
Washing, Water and Waste
I assume your city has people who wear clothes, get thirsty, and use the bathroom. The river will naturally be a super convenient place to dump your trash and, you know, take a dump. I'm sure some of your more well off citizens would want upstream water so that it doesn't taste so... earthy, or to wash their clothes where they know their neighbors don't dump their garbage. This means that more downstream city folks might find themselves more vulnerable to cholera, or in general get a dirtier river, causing more wealthier folks to try to move upstream.
Trade
Eventually, people in the one area of the city are going to realize it's really easy to move heavy objects if you put them on a raft than dragging it along by yourself. This will mean there will be warehouses and markets on the banks of the river. 87
Merchants will associate the river with more trade and more wealth. People will build up their houses around these markets, and then it comes to pass that the only way to really expand your business is to build up more river docks. This and the waste problem will cause people to:
Riverfront Spreading
It's a treat to be able to have riverfront property. The views are nicer, you get better breezes, quicker access to water, your own little private quay. People will grab property on the riverfront, and as your city develops, more and more people will have to build farther and farther up and down the river to grab that good riverfront property.
A river will also make people move downstream, eventually leading people to an ocean, lake, or sea. Here are some reasons why:
Floods
There will naturally be periods of heavy rainfall, and since lots of people have their houses built on the river (some of them perhaps less well off than others), naturally some of these buildings would be swept away in floods. Since floods cause things to go, you know, downstream, plenty of people will have reasons to go downstream to go look for their loved ones or to try to recover valuables that have been washed away. You don't need floods either, plenty of people might fall in the river after a night of drinking or have boats capsize, for people to want to look downstream.
Curiosity
This is the biggest one. Once it's super easy to go downstream (just get in a raft and go!) people would want to. Some of them might be thieves who want to avoid the law. Some of them would hear about vast treasures to be had downstream. The river, cutting itself through the vast landscape, would be an inescapable lure, pointing itself down and out, away from everything you've ever known and giving you a path to follow into the unknown.
This means, that as people spread out along the river and travel up and down it and more importantly down the river, you're eventually going to end up at a sea or lake or ocean. Then, everything that made the river so appealing to follow will be cranked up to overdrive as people move up and down the shore in both directions, and eventually people would be so interested in what is beyond the sea/lake/ocean that they build big honking ships to go and try to see what's on the other side.
If this whole scenario super plausible that's because this is exactly how early civilizations evolved and expanded. 87