Yes, the first series of questions are how big and how deep. There are many geophysical methods that may work depending on your answers. Electrical conductivity profiling may work for relatively shallow targets (<20 ft), magnetometry may work for slightly larger and deeper targets if the background soil is magnetic or if there are large ferrous targets in the cave. Electrical resistivity can work depending on the size and depth. Seismic reflection or refraction may work depending on size and depth. Gravity surveys might work as well.