We present a design for large rotating liquid mirrors. These mirrors a
re stiff lightweight structures designed to support a thin reflective
mercury surface layer. The general design features and fabrication tec
hniques are described and approximate analytic formulas are derived de
scribing the flexural, vibrational, and stability characteristics of t
hese mirrors. As an example, we describe in detail the 2.7-m mirror of
the UBC/Laval liquid mirror observatory. We conclude by considering t
he feasibility of employing this design for very large liquid mirrors.