Linnamäki is an ancient hillfort located in close proximity to Porvoo's Old Town.
The area consists of two hillforts north of Old Porvoo. Iso Linnamäki (Great Hillfort) is the site of one of Finland's largest ancient fortresses (or rather, its ruins), while Pikku Linnamäki (Little Hillfort) is home to an Iron Age burial site discovered in 1965. Iso Linnamäki is crisscrossed by many paths, and there are still dried-up moats with wooden bridges over them.
At the foot of the Linnamäki Hills lies Maari Park, a popular spot for walks and picnics among Porvoo residents.