  We present a versatile electric trap for the exploration of a wide range of
quantum phenomena in the interaction between polar molecules. The trap combines
tunable fields, homogeneous over most of the trap volume, with steep gradient
fields at the trap boundary. An initial sample of up to 10^8 CH3F molecules is
trapped for as long as 60 seconds, with a 1/e storage time of 12 seconds.
Adiabatic cooling down to 120 mK is achieved by slowly expanding the trap
volume. The trap combines all ingredients for opto-electrical cooling, which,
together with the extraordinarily long storage times, brings field-controlled
quantum-mechanical collision and reaction experiments within reach.
