rotundas

n. [ Cf. It. rotonda, F. rotonde; both fr. L. rotundus round. See Rotund, a. ] (Arch.) A round building; especially, one that is round both on the outside and inside, like the Pantheon at Rome. Less properly, but very commonly, used for a large round room; as, the rotunda of the Capitol at Washington. [ 1913 Webster ]