The installation "Invisible Spruce" (2020) was completed in collaboration between artists Pille Kivihall, Merle Suurkask, Eero Kotli, Hopner House and Catherine Guild. Located in St. Catherine's Church in Tallinn, Estonia.

Inspired by many important things that are often invisible to us and from St. Catherine's Church and its special atmosphere. This is how the spruce matured invisibly in the church of Catherine at the beginning of winter and Christmas time.