An aerodynamic investigation of cylindrical and Y-shaped building structures was carried out. Specific emphasis was directed towards determining the pressure distribution over three configurations: a flat top, a single dome and a dome with a counter-dome. The Y-model was tested in all three configurations while the cylindrical model was tested in dome/counter-dome configuration only. Both models were tested at Reynolds number(Re) of 360000 and 720000. Surface flow visualization was carried out to reveal regions of separation, recirculation and reattachment. It was found that a large region of negative pressure can be achieved with the dome counter-dome configuration. The maximum negative Cp for this configuration was about 50% higher than the maximum value observed with the flat top or single dome configuration. When the gap between the dome was decreased the maximum negative Cp increased; the increment being greater at the lower Re. Also, for the same Re and gap, the dome with higher curvature showed higher maximum negative Cp; the difference being more pronounced at the lower Re. The effect on the pressure distribution of an opening in the center of the lower dome and of an air flow through that opening was also investigated. It was observed that for injection rates corresponding to typical design flow rates required for ventilation of tall full scale buildings, the pressure distribution remains essentially unaltered. / Master of Science