Krstionica Sv. Trojstva (Baptismal Font of the Holy Spirit)

In Christian religious architecture, symbolism often starts with the first design step: the floor plan. Cruciform (cross-shaped) plans have been popular for centuries. Sometimes the entire church will be laid out on a cross. Sometimes crosses appear in other parts of the church, such as the nave. 

Polygons about in church architecture; Norway is filled with octagonal churches, and hexagonal churches can be found around the world. These were often intended to offer unobstructed views and more closeness than a cruciform building. Numerical symbology is found in almost every major religion, and Christianity is no exception. The hexagons and octagons represent important religious numbers: six and eight. But a heptagonal, or seven-sided, church is rarer.

Located in Rovinj, Croatia, the Baptismal Font of the Holy Spirit is a rare example of a seven-sided church. The Romanesque building dates back to the 12th century. The Catholic baptistery is considered the oldest building in this Istrian peninsula town.

Although usually closed, its interior features some additional details of interest. Carvings around the baptismal font are particularly noted for their detailing. The building is "the only Romanesque cultural object of neo-Latin style in all coastal Istria from the 13th century," according to the town's website.