The remains of the Roman aqueduct – one of the best preserved of northern Italy – imposing and well-known, still stand just outside the contemporary residential area, along the Bormida stream and their construction can be dated back, as it is highly likely, to the first imperial times, perhaps even to the Augustan era (early 1st century AD).
Two separate large parts of the original above-ground structure still exist, respectively made up of seven and eight masonry pillars, quadrangular in shape (measuring between 180 and 300 cm on their side, in proportion to the vertical development of the same pillars) that become progressively smaller upwards with a series of regular offsets, with a height of about 15 metres. Diminished arches rest on the pillars (there are only four left) of 3.35 metres radius, above which ran the water pipe itself, which no longer exists. The route of the aqueduct covers a total length of about 12 kilometres, starting from the water catch basin located in the Lagoscuro area (today in the municipal district of Cartosio), through the Erro valley (along the orographic right side of the stream with the same name), Marchiolli region up to the left bank of the Bormida river, with a total difference in height of about 50 metres.References:
First record of Kastelholma (or Kastelholm) castle is from the year 1388 in the contract of Queen Margaret I of Denmark, where a large portion of the inheritance of Bo Jonsson Grip was given to the queen. The heyday of the castle was in the 15th and 16th centuries when it was administrated by Danish and Swedish kings and stewards of the realms. Kastelhoma was expanded and enhanced several times.
In the end of 16th century castle was owned by the previous queen Catherine Jagellon (Stenbock), an enemy of the King of Sweden Eric XIV. King Eric conquered Kastelholma in 1599 and all defending officers were taken to Turku and executed. The castle was damaged under the siege and it took 30 years to renovate it.
In 1634 Åland was joined with the County of Åbo and Björneborg and Kastelholma lost its administrative status.