The whole area from Koartango to Zigoitia is characterised by its own local variant of Romanesque architecture. Buildings in this style can be found all over the municipality, though the most significant are in Zestafe, Ondategui and Gopegi.
Two of the best examples of local Romanesque buildings are to be found in the village of Zestafe: the parish church of San Nicolas dates from the 13th century, and features typical local Romanesque decoration on the eaves and around the portico and lights. It also houses and 13th century carved figure of the Virgin Mary in a style known in Basque as "Andra Mari".
The chapel of San Pedro de Gorostiza, which has recently been restored, is the oldest church in the area. It conserves pre-Romanesque tombs and reliefs on its walls.
The church of San Lorenzo in Ondategui is an extraordinary building with a Romanesque nave and portico and a transept and sanctuary end dating from the 17th century, featuring a magnificent Baroque main altar-piece and a secondary altar-piece with a 14th century "Andra Mari".
In the context of religious art, two later churches also stand out as particularly fine: the Neo-classical parish church of San Martín in Manurga (18th century) is a beautiful building with several fine altar-pieces and carvings.
The church of San Bartolomé in Olano was originally built in the Romanesque style, as some parts of it still evidence, but it stands out for its 16th century Gothic main altar-piece, made up of painted boards, reliefs and carvings of great value.
The parish church of San Lorenzo is an extraordinary building which is partly Romanesque (main body of the church and the doorway) and partly 17th century (transept and sanctuary end). It contains a magnificent Baroque main altarpiece and a second altarpiece on the altar of the Virgin Mary which features a 14th century carving of the type known as "Andra Mari" ("Our Lady" in Basque).