From the September 14th edition of the Economist:
George MacKerron and Susana Mourato from University College London and the London School of Economics recently looked at the relationship between happiness and nature. They found that people are happier in all outdoor environments (except in fog or rain) than they are indoors. What makes them happiest is taking exercise or bird-watching by the sea or on a mountain with someone they like. Those seeking to cheer themselves up should avoid bare inland areas, suburbia and children.