Ring Around a Tree by Tezuka Architects is a dual-purpose annex building at Fuji Kindergarden in Tachikawa, Tokyo, Japan. Located adjacent to the existing school, the structure functions as both English-language classrooms and as a waiting station for school buses. 

Permeated by wandering branches and overgrown foliage, the structure looks to destroy the boundaries between internal and external, and built and natural environments. Seven staggered floor plates modestly surround the mature and twisting tree, its columns and stairways dissolved into the shadows of the leaves and hardwood. 

Contained within a five meter height, the open, treehouse-like structure features a series of compressed and enclosed spaces accessible only to crouching, crawling children. The offset platforms are covered in soft rubber mats that help cushion the small, tender bodies from inevitable accidents. 

ShinkenchikuSha (Youtube)