diff --git a/nbt/world.py b/nbt/world.py
new file mode 100644
index 0000000..4dadaf6
--- /dev/null
+++ b/nbt/world.py
@@ -0,0 +1,167 @@
+"""Handle a world folder, containing """
+
+import os, glob, re
+from . import region
+from . import chunk
+
+class Format(object):
+	# format constants
+	INVALID     = -1  # Unknown or invalid world folder format
+	ALPHA       = 1   # Unsupported
+	MCREGION    = 2   # "Beta" file format
+	ANVIL       = 3   # Anvil file format, introduced in Minecraft 1.2
+
+
+class UnknownWorldFormat(Exception):
+	"""Unknown or invalid world folder"""
+	def __init__(self, msg):
+		self.msg = msg
+
+class WorldFolder(object):
+	def __init__(self, world_folder, format=None):
+		self.worldfolder = world_folder
+		self.format = format
+		os.listdir(world_folder) # Trigger OSError for non-existant directories or permission errors.
+		mcregion_fn  = list(glob.glob(os.path.join(world_folder,'region','r.*.*.mcr')))
+		anvil_fn     = list(glob.glob(os.path.join(world_folder,'region','r.*.*.mca')))
+		if self.format == None:
+			if (len(anvil_fn) > 0):
+				self.format = Format.ANVIL
+				regionfiles = anvil_fn
+			elif (len(mcregion_fn) > 0):
+				self.format = Format.MCREGION
+				regionfiles = mcregion_fn
+			else:
+				raise UnknownWorldFormat("Empty world or not a McRegion or Anvil format")
+		elif self.format == Format.ANVIL:
+			if len(anvil_fn) == 0:
+				raise UnknownWorldFormat("Empty world or not a Anvil format")
+			regionfiles = anvil_fn
+		elif self.format == Format.MCREGION:
+			if len(mcregion_fn) == 0:
+				raise UnknownWorldFormat("Empty world or not a McRegion format")
+			regionfiles = mcregion_fn
+		else:
+			raise UnknownWorldFormat("Unsupported world format")
+		self.regionfiles = {}
+		for filename in regionfiles:
+			m = re.match(r"r.(\-?\d+).(\-?\d+).mc[ra]", os.path.basename(filename))
+			if m:
+				x = int(m.group(1))
+				z = int(m.group(2))
+			else:
+				raise UnknownWorldFormat("Unrecognized filename format %s" % os.path.basename(filename))
+			self.regionfiles[(x,z)] = filename
+		self.regions     = {}
+		self.chunks      = None
+
+	def get_regionfiles():
+		"""return a list of full path with region files"""
+		return self.regionfiles.values()
+	
+	def get_region(self, x,z):
+		"""Get a region using x,z coordinates of a region. Cache results."""
+		if (x,z) not in self.regions:
+			if (x,z) in self.regionfiles:
+				self.regions[(x,z)] = region.RegionFile(self.regionfiles[(x,z)])
+			else:
+				# Return an empty RegionFile object
+				# TODO: this does not yet allow for saving of the region file
+				self.regions[(x,z)] = region.RegionFile()
+		return self.regions[(x,z)]
+	
+	def iter_regions(self):
+		for x,z in self.regionfiles.keys():
+			yield self.get_region(x,z)
+
+	def iter_chunks(self):
+		"""Returns an iterable list of all chunks. Use this function if you only 
+		want to loop through the chunks once or have a very large world."""
+		# TODO: Implement BoundingBox
+		# TODO: Implement sort order
+		for region in self.iter_regions():
+			for c in region.iter_chunks():
+				yield chunk.Chunk(c)
+
+	def get_chunk(self,x,z):
+		"""Return a chunk specified by the chunk coordinates x,z."""
+		# TODO: Implement (calculate region filename from x,z, see if file exists.)
+		rx,x = divmod(x,32)
+		rz,z = divmod(z,32)
+		return chunk.Chunk(self.get_region(rx,rz).get_chunk(x,z))
+	
+	def get_chunks(self, boundingbox=None):
+		"""Returns a list of all chunks. Use this function if you access the chunk
+		list frequently and want to cache the result."""
+		if self.chunks == None:
+			self.chunks = list(self.iter_chunks())
+		return self.chunks
+	
+	def chunk_count(self):
+		c = 0
+		for r in self.iter_regions():
+			c += r.chunk_count()
+		return c 
+	
+	def get_boundingbox(self):
+		"""Return minimum and maximum x and z coordinates of the chunks."""
+		b = BoundingBox()
+		for rx,rz in self.regionfiles.keys():
+			region = self.get_region(rx,rz)
+			rx,rz = 32*rx,32*rz
+			for cc in region.get_chunk_coords():
+				x,z = (rx+cc['x'],rz+cc['z'])
+				b.expand(x,None,z)
+		return b
+	
+	def cache_test(self):
+		"""Debug routine: loop through all chunks, fetch them again by coordinates, and check if the same object is returned."""
+		# TODO: make sure this test succeeds (at least True,True,False, preferable True,True,True)
+		# TODO: Move this function to test class.
+		for rx,rz in self.regionfiles.keys():
+			region = self.get_region(rx,rz)
+			rx,rz = 32*rx,32*rz
+			for cc in region.get_chunk_coords():
+				x,z = (rx+cc['x'],rz+cc['z'])
+				c1 = chunk.Chunk(region.get_chunk(cc['x'],cc['z']))
+				c2 = self.get_chunk(x,z)
+				correct_coords = (c2.get_coords() == (x,z))
+				is_comparable = (c1 == c2) # test __eq__ function
+				is_equal = (c1 == c2) # test if id(c1) == id(c2), thus they point to the same memory location
+				print x,z,c1,c2,correct_coords,is_comparable,is_equal
+	
+	def __str__(self):
+		return "%s(%s,%s)" % (self.__class__.__name__,self.worldfolder, self.format)
+
+
+class BoundingBox(object):
+	"""A bounding box of x,y,z coordinates"""
+	def __init__(self,minx=None, maxx=None, miny=None, maxy=None, minz=None, maxz=None):
+		self.minx,self.maxx = minx, maxx
+		self.miny,self.maxy = miny, maxy
+		self.minz,self.maxz = minz, maxz
+	def expand(self,x,y,z):
+		if x != None:
+			if self.minx is None or x < self.minx:
+				self.minx = x
+			if self.maxx is None or x > self.maxx:
+				self.maxx = x
+		if y != None:
+			if self.miny is None or y < self.miny:
+				self.miny = y
+			if self.maxy is None or y > self.maxy:
+				self.maxy = y
+		if z != None:
+			if self.minz is None or z < self.minz:
+				self.minz = z
+			if self.maxz is None or z > self.maxz:
+				self.maxz = z
+	def lenx(self):
+		return self.maxx-self.minx+1
+	def leny(self):
+		return self.maxy-self.miny+1
+	def lenz(self):
+		return self.maxz-self.minz+1
+	def __str__(self):
+		return "%s(%s,%s,%s,%s,%s,%s)" % (self.__class__.__name__,self.minx,self.maxx,
+				self.miny,self.maxy,self.minz,self.maxz)