The rock formation called “Kastelli Giant’s Church” in Pattijoki's Ylipää district is the largest of its kind in Ostrobothnia. Rectangular or oval boulder embankments, Giant’s Churches are the oldest prehistoric structures found in Finland. They were created by Stone Age people who shaped the rock walls formed on the ancient shores by natural forces to suit their own needs. Kastelli Giant’s Church is approximately 58 metres long and 36 metres wide, and shaped like a rectangle with rounded corners. The embankments are notably wide and, in parts, almost 1.5 metres high. Each side features openings that have been interpreted as gateways.
Giant’s Churches mostly date back to 3500–2000 BCE. At that point, people had settled down in specific locations more than before. During that time, people were mostly hunter-gatherers, but there seems to have been some farming activity too. Building a Giant’s Church was a massive undertaking for a community, which required a high level of collaboration and organisation. Originally, the formations were constructed on islands and shore areas, but due to post-glacial rebound, they are now located inland. There are 40 known Giant’s Churches, with as many as eight of them in Raahe.
How to visit: Set the navigator to Linnalantie 74. The "Linnanraunio" guide signs are also helpful, even though it's not about the castle ruins, linnanrauniot. There is a parking lot a couple of hundred meters away and the forest road leading to the ancient remains is clearly marked. There is a outhouse by the parking lot, and in the area there is a geocache and a group of tables for a snack.