Westminster Abbey:

Inner and outer vestibules lead to the octagonal chapter house, which is of exceptional architectural purity. It is built in a Geometrical Gothic style with an octagonal crypt below. A pier of eight shafts carries the vaulted ceiling. To the sides are blind arcading, remains of 14th-century paintings and numerous stone benches above which are innovatory large 4-light quatre-foiled windows. These are virtually contemporary with the Sainte-Chapelle, Paris.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". There is an octagonal what above the chapter house?
unanswerable