diff --git a/geos.cabal b/geos.cabal
--- a/geos.cabal
+++ b/geos.cabal
@@ -1,7 +1,7 @@
 cabal-version:       2.2
 name:                geos
 
-version:             0.3.0
+version:             0.4.0
 
 synopsis:  Bindings for GEOS.
 
@@ -40,7 +40,8 @@
     , vector
     , transformers
     , mtl
-  build-tools: hsc2hs
+  build-tool-depends:
+    hsc2hs:hsc2hs
   exposed-modules:
       Data.Geometry.Geos.Topology
     , Data.Geometry.Geos.Geometry
@@ -86,7 +87,8 @@
     exitcode-stdio-1.0
   default-language:    Haskell2010
   hs-source-dirs: tests src
-  build-tools: hsc2hs
+  build-tool-depends:
+    hsc2hs:hsc2hs
   main-is: Main.hs
 
   build-depends:
@@ -116,6 +118,7 @@
     , Data.Geometry.Geos.Raw.Topology
     , Data.Geometry.Geos.Raw.STRTree
     , Data.Geometry.Geos.Raw.Prepared
+    , Data.Geometry.Geos.Prepared
     , Data.Geometry.Geos.Relatable
     , Data.Geometry.Geos.Serialize
     , Data.Geometry.Geos.Topology
@@ -123,6 +126,7 @@
     , Data.Geometry.Geos.TopologySpec
     , Data.Geometry.Geos.RelatableSpec
     , Data.Geometry.Geos.SerializeSpec
+    , Data.Geometry.Geos.STRTreeSpec
     , Helpers
 
 source-repository head
diff --git a/src/Data/Geometry/Geos/STRTree.hs b/src/Data/Geometry/Geos/STRTree.hs
--- a/src/Data/Geometry/Geos/STRTree.hs
+++ b/src/Data/Geometry/Geos/STRTree.hs
@@ -17,14 +17,12 @@
   , toList
   , toVector
   , fromList
-  , empty
-  , build
-  , insert
+  , unfoldr_
+  , unfoldr
   , fromFoldable
   , fromFoldable_
   , lookup
   , RT.STRTree
-  , RT.STRTreeBuilder
   )
 where
 
@@ -55,17 +53,23 @@
 fromList :: Storable b => [(Geometry a, b)] -> RT.STRTree b
 fromList = fromFoldable
 
-empty :: RT.STRTreeBuilder a
-empty = runGeos $ RT.createSTRTreeBuilder 10
-
-build :: RT.STRTreeBuilder a -> RT.STRTree a
-build = runGeos . RT.build
+unfoldr :: Storable a => (b -> Maybe ((Geometry g, a), b)) -> b -> RT.STRTree a
+unfoldr = unfoldr_ 10
 
-insert :: Storable a => Geometry b -> a -> RT.STRTreeBuilder a -> ()
-insert geom item tree = runGeos $ do
-  rg :: RG.GeomConst <- convertGeometryToRaw geom
-  RT.insert tree rg item
-  return ()
+unfoldr_ :: Storable a => Int -> (b -> Maybe ((Geometry g, a), b)) -> b -> RT.STRTree a
+unfoldr_ capacity func initial = runGeos $ do
+  builder' <- RT.createSTRTreeBuilder capacity
+  go builder' func initial
+  where
+    go builder f init' =
+      case f init' of
+        Just ((geom, item), next) -> do
+          rg :: RG.GeomConst <- convertGeometryToRaw geom
+          RT.insert builder rg item
+          go builder f next
+        Nothing -> do
+          tree <- RT.build builder
+          pure tree
 
 {-|
 `fromFoldable` creates an STRTree with a default node capacity of 10. For finer-grained control over the node capacity, `fromFoldable_` accepts a node-capacity argument.
diff --git a/tests/Data/Geometry/Geos/STRTreeSpec.hs b/tests/Data/Geometry/Geos/STRTreeSpec.hs
new file mode 100644
--- /dev/null
+++ b/tests/Data/Geometry/Geos/STRTreeSpec.hs
@@ -0,0 +1,52 @@
+module Data.Geometry.Geos.STRTreeSpec where
+
+import Data.Either
+import qualified Data.Vector as V
+import qualified Data.Geometry.Geos.STRTree as STR
+import Data.Geometry.Geos.Geometry
+import           Test.Hspec
+
+strSpec = describe "STRTree" $ do
+  describe "fromList" $ do
+    it "should correctly build an STRTree" $ do
+      let points = fmap (flip PointGeometry Nothing . point . uncurry coordinate2)
+            [ (0.1, 0.2)
+            , (0.2, 0.3)
+            , (0.3, 0.4)
+            ]
+          mapping :: [(Geometry Point, Int)]
+          mapping = zip points [1..]
+          strtree = STR.fromList mapping
+          env = V.fromList $ fmap (uncurry coordinate2)
+            [ (0, 0)
+            , (1, 0)
+            , (1, 1)
+            , (0, 1)
+            , (0, 0)
+            ]
+          eitherQuery = linearRing  env >>=  polygon . V.singleton
+          query = PolygonGeometry (fromRight (error "shouldn't happen") eitherQuery) Nothing
+          results = STR.lookup query strtree
+      results `shouldBe` (V.fromList [1..3])
+
+  describe "unfoldr" $ do
+    it "should correctly build an STRTree" $ do
+
+      let buildFunc i =
+            if i < 1
+               then Just ((flip PointGeometry Nothing . point $ coordinate2 i i, 100 + i), i+0.1 )
+               else Nothing
+          init :: Double
+          init = 0.1
+          strtree = STR.unfoldr buildFunc init
+          env = V.fromList $ fmap (uncurry coordinate2)
+            [ (0, 0)
+            , (1, 0)
+            , (1, 1)
+            , (0, 1)
+            , (0, 0)
+            ]
+          eitherQuery = linearRing  env >>=  polygon . V.singleton
+          query = PolygonGeometry (fromRight (error "shouldn't happen") eitherQuery) Nothing
+          results = STR.lookup query strtree
+      V.length results `shouldBe` 10
diff --git a/tests/Data/Geometry/Geos/SerializeSpec.hs b/tests/Data/Geometry/Geos/SerializeSpec.hs
--- a/tests/Data/Geometry/Geos/SerializeSpec.hs
+++ b/tests/Data/Geometry/Geos/SerializeSpec.hs
@@ -27,12 +27,6 @@
 multiLineStringNoSRID = MultiLineStringGeometry (fromRight $ makeMultiLineString  [[(544066.685319362, 6892760.57728029), (544051.856441192, 6892739.65385582), (544035.191589876, 6892723.54713431), (544034.932084016, 6892723.39918434)]]) Nothing
 
 
---loadThingsFromFile :: FilePath -> IO [Some Geometry]
---loadThingsFromFile fp = do
---  rows <- BS8.readFile fp
---  return $ catMaybes $ readHex <$> (BS8.lines rows)
-
-
 serializeSpec = describe "Serialize" $ do
   describe "readHex" $ do
     it "should convert a WKB bytestring to a geometry" $ (readHex multiLineStringWKB >>= ensureMultiLineString)  `shouldBe` Just multiLineString1
diff --git a/tests/Main.hs b/tests/Main.hs
--- a/tests/Main.hs
+++ b/tests/Main.hs
@@ -6,9 +6,11 @@
 import Data.Geometry.Geos.TopologySpec
 import Data.Geometry.Geos.RelatableSpec
 import Data.Geometry.Geos.SerializeSpec
+import Data.Geometry.Geos.STRTreeSpec
 
 main :: IO ()
 main = hspec $ do
   topologySpec
   relatableSpec
   serializeSpec
+  strSpec