Nope, these aren't corn cobs. In green construction, cob refers to a mixture of earth and straw similar to the adobe homes you might see in the American southwest. Cob is an inexpensive, versatile material that allows builders to shape walls any way they want. While adobe is usually formed into bricks or blocks, cob is unique in that it's applied in large handfuls to form the structure.
Typical cob homes have unique, rounded features and almost look like they're made out of clay -- that's probably because they basically are! And cob is sturdier than you might think: Some cob homes built in England in the 19th century are still around today.