diff --git a/coordinates/src/bin/default_map.rs b/coordinates/src/bin/default_map.rs
new file mode 100644
index 0000000..ec946a4
--- /dev/null
+++ b/coordinates/src/bin/default_map.rs
@@ -0,0 +1,32 @@
+use coordinates::hex_map;
+use std::path::PathBuf;
+
+#[derive(Clone)]
+struct MapVal;
+
+impl Default for MapVal {
+    fn default() -> Self {
+        Self
+    }
+}
+
+impl From<MapVal> for String {
+    fn from(_val: MapVal) -> Self {
+        ".".to_owned()
+    }
+}
+
+fn main() {
+    let mut args = std::env::args().skip(1);
+
+    let filename = args
+        .next()
+        .map(|p| PathBuf::from(p))
+        .expect("A filename is required");
+    let size = args
+        .next()
+        .and_then(|s| s.parse::<usize>().ok())
+        .unwrap_or(3);
+    let map: hex_map::Map<MapVal> = hex_map::Map::new_hexagonal(size);
+    hex_map::write_file(filename, map);
+}
diff --git a/coordinates/src/hex_map.rs b/coordinates/src/hex_map.rs
index 1291c69..72ff9cc 100644
--- a/coordinates/src/hex_map.rs
+++ b/coordinates/src/hex_map.rs
@@ -67,7 +67,9 @@ where
     std::fs::write(path, write_data(map).join("\n")).map_err(Error::from)
 }
 
-fn parse_data<'a, A: Default + From<String>>(data: impl Iterator<Item = &'a str> + 'a) -> Map<A> {
+pub fn parse_data<'a, A: Default + From<String>>(
+    data: impl Iterator<Item = &'a str> + 'a,
+) -> Map<A> {
     fn parse_line<A: From<String>>(input: &str) -> Result<(AxialAddr, A), nom::error::Error<&str>> {
         fn parse<A: From<String>>(input: &str) -> IResult<&str, (AxialAddr, A)> {
             let (input, addr) = parse_address(input)?;