For some of the effects of these landmarks, you may need to wait. What better way than to sit down? Hold Spacebar, and you sit down. There you go. That's really all there is to it. Just move when you want to get back up.

The Stone Circle is located somewhere on the island. It is probably the most important landmark of the game as it is the only way to progress the game into different seasons. (Which is how you win the game.) Basically, it is a circle of stones. This may be hard to notice. However, the effect does not activate until it turns night for the first time during a season. (It does not work at all for the Winter season.) When it does, there will be particles gathering at this circle. (If you are having a hard time finding it, you can see a trail of particles from the sky leading down to where the stone circle is from any mountain. This trail is very difficult to notice in Autumn, so memorize the location in Spring and Summer. Alternatively, there should be a straight-ish line of stones. It naturally leads to the stone circle, so if you follow the line, you should come across the circle. If not, reverse directions down the line.) The particles will make a smaller circle inside the stone circle. This circle speeds up time. The closer you get, the faster time will flow. You can use this to speed up time so you can enjoy the Day and Night events a season has to offer. If you enter the circle, you progress to the next season. Spring->Summer->Autumn->Winter.

[More Information on Stone Circles:]
[More Information on Stone Circles]

The Big Tree is the only landmark I believe that changes with the seasons, as it is a tree. For example, the Big Tree is a dead Big Tree in Winter. At Night during the Autumn season, the area underneath the Big Tree is beautifully lit up. If you wait around a while, a sparkling fox head may make an appearance from behind a small tree around the big tree. It will pop out for a while, and then hide again. (It may go back into hiding if approached as well.)

The Cabin's effect occurs at Night during the Autumn season. The area is uniquely lit up. All the particles sort of stop in time. That is all I have found out about it thus far.

Towers (also known as Castles by some.) are used for teleportation, surprisingly. (It works in all seasons, with the possible exception of Winter.) You pick a side on the Tower, walk into it, and the screen will fade to black. You teleport between Towers, so this will require more than one Tower on the map. (I've personally encountered a maximum of five Towers at a time.) In Autumn, at Night, the Towers will light up the sky with their pattern when you are near them. For example, if one side is destroyed, that pattern will be reflected on the sky. The area also turns into a sihouette. You can still teleport, but you will not notice the screen fade making it hard to identify when you have teleported.

The Graveyard has a cluster of particles form endlessly around it at Night in Autumn. (These clusters form elsewhere is Autumn at Night, but they seem to sprout up every few seconds at the Graveyard.) It is also lit up a little bit. There are unidentified red sprites normally near one tombstone. (I think this may be the remains of some effect that may occur in the Summer.)

High up on the mountain tops, there is a Totem Circle. Unlike the other Landmarks, it has an effect in the Spring/Summer as well. At Night, the stars in the sky will begin to explode. In Autumn at Night, this effect also occurs, but the sky now turns red. You will begin to emit a trail of particles that fades away. If you wait a while, you will stop emitting the trail, and the rest of the particles will fly up into the sky. Afterwards, the stars will stop exploding, and if you back away, the sky will revert back to normal, and a man will appear, who emits a trail of particles that fade. He will run away. (On smaller islands, he appears to run away to the Big Tree.)