Insect and Spider Identification: CLOSED: Strange bee nest, 1 by MaryE

MaryE wrote:
It's stuck to the underside of the window frame and to the house, is 7 inches long overall with the bulbous part of the nest being about 2 inches wide and 2 inches high. A black and white insect about the size of a bumblebee flew to it, went inside and a couple of minutes later flew away. The nest is made of paper pulp. Above the bulbous part it has a separate little roof for rain protection. Anybody ever see anything like it? I never have. What insect made it?