An architect helps the gang rebuild their tree house. Arthur's chorus group has a new teacher.
Carved from 100 million pounds of stone, soaring effortlessly atop a spiderweb of masonry, Gothic cathedrals are marvels of human achievement and artistry. But how did medieval builders reach such spectacular heights? Consuming the labor of entire towns, sometimes taking 100 years to build, these architectural marvels were crafted from just hand tools and stone.