the 1929 Caproni Ca.90, a six-engined inverted sesquiplane. In 1929 it was the largest aircraft in the world, it held that record until 1934

A six-engined inverted sesquiplane designed as a heavy bomber, read more about it and see a couple more photos at: http://dieselpunks.blogspot.com/2010/07/italian-giant.html