Tourism today has become rather specialized. In addition to the general tours, which only allow the traveler to quickly visit one or two heritage sites and do a little shopping on the side, innovative travel agencies offer a number of itineraries for people with special interests. For modern-day religious pilgrims, trips are arranged to Jerusalem and Mecca. For people who are interested in nature, ocean liners retrace the voyages taken by the naturalist Charles Darwin. Nature lovers can also take ecological tours that teach how to distinguish the plant and insect life in preserved wetlands. One of the newer types of tourism is called dark tourism, which includes tours to cemeteries and prisons. The traveler can visit the tombs of famous people at a cemetery in Paris or visit prisons where well-known political prisoners or hardened criminals were imprisoned. For people who take such specialized tours, learning something is more important than just being able to say, "I've been there."