Abstract Oval, circular and elliptic forms appear in the architecture from the very beginning. The basic problem of the geometric analysis of the spaces with an elliptic or oval ground plan is a great sensitivity of the outcome calculations to the plan's precision, mainly to distinguish between oval and ellipse. Sebastiano Serlio and Guarino Guarini belong to those architects, theoreticians, who analysed the potential of circular or oval forms and some of their ideas are analysed in the paper. Elliptical or oval plans were used also in Slovak baroque architecture or interior elements and the paper introduce some of the most known examples as a connection to the world architecture ideas.