Electron micrograph of negatively stained Ad2 (source, K. Boucke).  For further information see (1; 2).

(1). Valentine, R. C., and Pereira, H. G. (1965) J. Mol. Biol. 13, 13-20.
(2). Greber, U. F., et al. (1998) in Adenovirus entry into cells: A quantitative fluorescence microscopy approach, ed. W. S. M. Wold (Humana Press, Inc, Totowa, NJ USA), pp. 217-230.