Through outside influences, Thailand has a rich diversity of architectural wonders. Religion, art and architecture were traditionally inseparable, and house, temple and stupa designs adhered to strict rules. Religious architecture varies between regions: northern temples borrow from Lao, Lanna, Burmese and Mon styles, while Mon and Khmer influences prevail in the northeast. Central Thailand is famous for its Sukhothai and Ayutthaya styles, and these evocative ancient cities are now historical parks.