diff --git a/cmd/mtredisalize/leveldb.go b/cmd/mtredisalize/leveldb.go
index 23c8109..f8ede70 100644
--- a/cmd/mtredisalize/leveldb.go
+++ b/cmd/mtredisalize/leveldb.go
@@ -14,11 +14,13 @@ import (
 )
 
 type LevelDBBackend struct {
-	cache         *leveldb.Cache
-	db            *leveldb.DB
-	interleaved   bool
-	encoder       common.KeyTranscoder
-	decoder       common.KeyTranscoder
+	cache       *leveldb.Cache
+	db          *leveldb.DB
+	interleaved bool
+	coverage    *common.Coverage3D
+	encoder     common.KeyTranscoder
+	decoder     common.KeyTranscoder
+
 	changeTracker *ChangeTracker
 	mutex         sync.RWMutex
 }
@@ -71,9 +73,42 @@ func NewLeveDBBackend(
 		encoder:       encoder,
 		decoder:       decoder,
 		changeTracker: changeTracker}
+
+	if !interleaved {
+		if err = ldb.buildCoverage(); err != nil {
+			ldb.Shutdown()
+			ldb = nil
+			return
+		}
+	}
 	return
 }
 
+func (ldb *LevelDBBackend) buildCoverage() error {
+	log.Println("INFO: Start building coverage index (this may take some time)...")
+
+	coverage := common.NewCoverage3D()
+
+	ro := leveldb.NewReadOptions()
+	defer ro.Close()
+	ro.SetFillCache(false)
+	it := ldb.db.NewIterator(ro)
+	it.SeekToFirst()
+	for ; it.Valid(); it.Next() {
+		c, err := common.DecodeStringBytesToCoord(it.Key())
+		if err != nil {
+			return err
+		}
+		coverage.Insert(c)
+	}
+	if err := it.GetError(); err != nil {
+		return err
+	}
+	ldb.coverage = coverage
+	log.Println("INFO: Finished building coverage index.")
+	return nil
+}
+
 func (ldb *LevelDBBackend) doRead(f func(db *leveldb.DB)) {
 	ldb.mutex.RLock()
 	f(ldb.db)
@@ -156,6 +191,13 @@ func (ldbs *LevelDBSession) Store(hash, key, value []byte) (exists bool, err err
 	})
 	// This technically too early because this done in transactions
 	// which are commited (and possible fail) later.
+	if ldbs.backend.coverage != nil {
+		c, err := common.DecodeStringBytesToCoord(origKey)
+		if err != nil {
+			return false, err
+		}
+		ldbs.backend.coverage.Insert(c)
+	}
 	if ldbs.backend.changeTracker != nil {
 		ldbs.backend.changeTracker.BlockChanged(origKey)
 	}