Roughly rectangular in shape, Oz is divided along the diagonals into four countries: Munchkin Country in the East, Quadling Country in the South, Winkie Country in the West and Gillikin Country in the North. There is also a fifth nation in the Northwest, Ugabu. These surround the Emerald City in the center. It is surrounded on all four sides by a desert. If someone touches it they instantly turn to sand. They are the Shifting Sands in the East, the Great Sandy Waste in the South, the Deadly Desert in the West and the Impasaible Desert in the North, which helps to protect it from discovery and invasion. It is further protected by a barrier of invisibility erected by Glinda. Oz is the largest country on the continent of Nonestica.
Oz as a place is incredibly demographically diverse, with wide varieties of ecology and huge diversity with the number of species and creatures which occupy the land. At least some of Oz's infrastructure is made of yellow brick. The general style of architecture varies by country.
Munchkin Country is the eastern quadrant of Oz inhabited by the Munchkins. It is shown to be mostly farmland but does include strange shapes hills and rock arches and the Dark Forest in the southern part of the country. After Evanora's true form was exposed she was banished from the Emerald City and became the tyrannical ruler of the Munchkins. The Munchkins were later freed when Evanora was crushed by Dorothy Gale's house. The color of Munchkin Country is blue.
Quadling Country is the southern quadrant of Oz inhabited by the Quadlings. It is a mostly mountainous country, but also features animal shaped rocks and shards of emerald crystals. It is ruled by Glinda, the Good Witch of the South from her palace. The country also has strange fauna like zebra print bird and giraffe creatures and pink, red and orange colored trees. The color of Quadling Country is red.
Winkie Country is the western quadrant of Oz inhabited by the Winkies. It is shown to be covered in farmland and forests but also has fields of flowers like poppies and sunflowers. In the north of the country there are towering rocky structures. After Theodora was banished from the Emerald City like her sister, Evanora, she became to ruler of the country. Like Munchkin Country, it was freed by Dorothy Gale. Dorothy freed Wnkie Country was melting Theodora after throwing a bucket of water on her. The color of Winkie Country is yellow.
Gillikin Country is the northern quadrant of Oz inhabited by the Gillikins. Little in known about the country other than that is is heavily forested and mountainous. It is also shown to have a large lake and a river that runs through the country. Theodora was said to the Good Witch of the North but later turned evil and became the Wicked Witch of the West. It is possible that Mombi is a Gillikin and originally lived in the country before becoming the 'princess' of Oz. The color of Gillikin Country is purple.
Very little is known about Ugabu. It is shown to be in the northwest of Oz meaning it may be part of Winkie Country, although it may be it's own country. It's possible that Oscar Diggs flew over Ugabu when he arrived in Oz.