From Lonely Planet: "Patan is separated from Kathmandu only by the Bagmati river and is the second largest town in the valley. It is often referred to as Lalitpur, which means 'city of beauty'. Patan has a long Buddhist history and the four corners of the city are marked by stupas said to have been erected by the great Buddhist emperor Ashoka around 250 BCE. Later inscriptions refer to palaces in the city in the 5th century CE although Patan's great building boom took place under the Mallas in the 16th, 17th and 18th centuries.
Patan's central Durbar Square is absolutely packed with temples; it's an architectural feast with a far greater concentration of temples per square metre than in Kathmandu or Bhaktapur. Numerous other temples of widely diverse style as well as many bahals (Buddhist monasteries) are scattered around this fascinating town."