The Mausoleum of Maussollos increases its builder's Golden Ages by fifty percent. It also increases the chances of a Great Artist appearing.
This wonder has little impact alone, but can be greatly useful if Golden Ages form a key part of your strategies. If you're emphasizing a particular type of Great Person, any other "waste" Great People can be used to start Golden Ages instead, and this wonder serves as compensation.
Alternatively, if you can afford to, aim to get both this wonder and the Taj Mahal, to emphasize the latter's bonus.
Maussollos died in 349 BC. King of Caria during his lifetime, Maussollos wished to leave a reminder of himself for future generations in the form of a great tomb. In addition to hiring hundreds of laborers, Maussollos commissioned five of the finest artisans in the Hellenic world to design the hundreds of statues that were to line the peripheries of his white marble resting place.
Over 130 feet tall upon completion, the Mausoleum of Maussollos stood by the harbor of Halicarnassus until 1522, when the Knights Hospitaller tore it down in order to use the stones to build defenses against the approaching Turks.