There may have been two or three wooden churches in Kökar since the last half of 14th century. During the 16th century a Franciscan monastery was founded on Hamnö island. This place became a spiritual and cultural centre for the entire archipelago.
Today the ruins of monastery share their site with current Kökar's church, which is probably third in this place. It was built between 1769 and 1784 in charge of Antti Piimänen (he died before church was completed). Stones of previous monasteries were used in the construction. In the chapel beside the church are archaeological excavations on Hamnö.
The Broch of Gurness is an Iron Age broch village. Settlement here began sometime between 500 and 200 BC. At the centre of the settlement is a stone tower or broch, which once probably reached a height of around 10 metres. Its interior is divided into sections by upright slabs. The tower features two skins of drystone walls, with stone-floored galleries in between. These are accessed by steps. Stone ledges suggest that there was once an upper storey with a timber floor. The roof would have been thatched, surrounded by a wall walk linked by stairs to the ground floor. The broch features two hearths and a subterranean stone cistern with steps leading down into it. It is thought to have some religious significance, relating to an Iron Age cult of the underground.
The remains of the central tower are up to 3.6 metres high, and the stone walls are up to 4.1 metres thick.