The Haitises caves in Sabana de la Mar area (on the eastern coast) are prepared for visits. (Tour sold by tour operators at hotels or this can be done by renting a car and visiting the National Parks Office in Sabana de la Mar.)
Also, by the end of March or start of April the Ministry of Environment is opening the Cueva de las Maravillas near to both La Romana and San Pedro de Macoris (Juan Dolio) destination areas, and not too far from Santo Domingo. This tour will probably be offered by tour operators working in the area. It is not yet open to the general public, but once it is ready there should be a big sign on the highway and it can be easily visited. Rent a car for the day.
For those staying in the East, there is the spectacular Fun Fun Cave. Rancho Capote offers excursions where visitors rapel down and then take a boat ride along the underground river that runs for an incredible seven kilometers. This excursion should be offered to tourists staying in East Coast hotels by tour operators working in the area.
The biggest cave in the DR is at Pomier, in southwestern San Cristobal, about half an hour drive from Santo Domingo. You will need to know Spanish, as the guides on site are Spanish-speaking. This is the largest cave in the Caribbean. Am not familiar with tour operators working this cave as it is still in the raw. Cave experts do offer guided tours in English. For those wanting to put together a group to visit this cave and others, send us an email to put you in contact with the cave experts that do guided tours.