VH → Locations → Onsen Town wall
Onsen Town is surrounded by a curtain wall, with gates in each cardinal direction. You are able to both go inside the wall and climb on top of it to travel around the perimeter of the city.
Onsen Town's North Gate is sealed when you first arrive. When you take the Goblin Extermination quest, the gate will automatically be unlocked. While you're on the quest, exiting the North Gate will take you directly to the camp site of the goblins you need to murder. After you've completed the quest, the North Gate remains unlocked and leads to the wilderness north of town. If you ever repeat the quest, the gate will once again lead directly to the goblin camp. It'll go back to letting you access the wilderness once the quest is complete.
You'll use this gate for the Goblin Extermination quest, of course, as well as part of the later Thieves' hide-out quest. In addition, after you reach the Capital and take the Rescue at Wyvern Valley quest, you'll return and head out this way.
The North Gate contains doors that lead inside the City Walls. Walk underneath the gate so that you're hidden from view and then go either east or west. If you have trouble, shift one square north or south and try again.
Also, note that on top of the wall there are small gaps in the battlements. If you're on top of the wall, you can jump down at those gaps to reach ground level. You can't climb back up through them, though.
The East Gate is sealed, but there's a gaping hole in the wall just to the north of it. Note the patches of sand, which indicate where so many people have walked around the gate that they've killed the grass. Why is the soldier facing the nice, secure gate to his south instead of the massive breach to his north? Because he is bad at his job.
Anyway, walking out this gate will take you to the wilderness east of town. This is the gate you'll use for the Bodyguard and Babysitter quests, as well as the first part of the Thieves' hide-out quest.
This gate also has doors that lead inside the Walls. One entrance is on the northern side of the hole, and the other is on the southern side of the gate itself.
The top of the East Gate has just one gap in the battlement, on the interior side. Once again, you can use this to jump down but not to get back up.
The South Gate was opened very recently; previously it was permanently locked. A little odd, since it appears to be the main gate, with what appear to be pretty beefy towers on either side.
The area to the south is currently very incomplete. At the moment, you'll just find a few screens of nothing-much. However, a signpost seems to indicate that this path will eventually take you to a town called Burukasa.
As with the other gates, there are doors that lead inside the Walls, and on top of the wall there is a gap in the battlement on the interior side.
The West Gate is open from the time you arrive. It leads to the wilderness west of town.
It has doors that lead inside the Walls, and on the top of the wall there are gaps you can jump down from on either side.
Inside the Wall
As mentioned above, it is possible to go inside the Wall by using entrances in each gate. Additionally, on top of the wall at each corner of town is a staircase leading inside. Finally, the interior can also be accessed from the dirt road next to the carriage shop that leads to the Horse Train station, because the station is essentially built into the wall.
By getting inside the northeast section of the Wall, you can get into the employee area of the City Guard headquarters.
Other than that, there is very little of interest in here.
There are exterior staircases at each corner of the city. You can use these to climb from ground level directly to the top of the wall.
The northeast and southwest staircases are accessible from town. Head for one of these for easy access to the area on top of the wall.
The staircase at the northwest corner of town is blocked off with a gate for some reason, but you can explore the area up there simply by using one of the other staircases and then running to the northwest side of top atop the wall.
The staircase at the southeast corner of town leads to a small island surrounded by the lake. This staircase is the only way to get there, so if you want to check the island out you'll need get on top of the wall, run to the southeast corner, and head down the stairs.
On top of the Wall
Once on top of the wall, you can run around the entire perimeter of the city. There's nothing much up here, other than some guards to chat with on the south side and a merchant to the north, so it's more of a way to get places than a destination in itself.