Mikasalla is a small, quiet town in the far south west of Osenia, west of Garoh. There is not much of interest in Mikasalla, its houses are modeled in the same style as Garoh and Yallam. By using Scoop in the south west corner of the town in a backyard, you can access a small cavern where you can, if you travel far enough, reach the MarsDjinni, Spark.
The lake in the small cavernous underground trail underneath the town reacts accordingly to the Parch Psynergy (in that the water disappears), but there is absolutely no further purpose in doing this beyond removing the lake. It is unknown what the developers had in mind with including a body of water that could be Parched in this particular location, whether it was intended to hide a secret or if it was just an Easter Egg.
One of the Colosso Gladiators, Galahad, can be encountered in Mikasalla's Inn if The Lost Age is being played with password data transfer from the previous Golden Sun, if Isaac fully won the Colosso tournament then. Galahad's initial conversation with Felix when talked to has him saying that Azart, Satrage and Navampa are searching for Isaac. Due to a glitch, however, if Galahad is Mind Read before being talked to normally, he will think the entire conversation.