diff --git a/chapter04/src/router_cities.js b/chapter04/src/router_cities.js
new file mode 100644
index 0000000..d4ea58a
--- /dev/null
+++ b/chapter04/src/router_cities.js
@@ -0,0 +1,27 @@
+/* @flow */
+"use strict";
+
+const express = require("express");
+
+const routerCities = express.Router();
+
+routerCities.get("/MVD", (req, res) => {
+    res.send(`GET Montevideo... path=${req.originalUrl}`);
+});
+
+routerCities.get("/:id", (req, res) => {
+    res.send(`GET City... path=${req.originalUrl}`);
+});
+
+routerCities.delete("/:id", (req, res) => {
+    res.send(`DELETE City... path=${req.originalUrl}`);
+});
+
+routerCities.post("/", (req, res) => {
+    res.send(`POST City... path=${req.originalUrl}`);
+});
+
+routerCities.put("/:id", (req, res) => {
+    res.send(`PUT City... path=${req.originalUrl}`);
+});
+module.exports = routerCities;
diff --git a/chapter04/src/router_countries.js b/chapter04/src/router_countries.js
new file mode 100644
index 0000000..fb1df6d
--- /dev/null
+++ b/chapter04/src/router_countries.js
@@ -0,0 +1,20 @@
+/* @flow */
+"use strict";
+
+const express = require("express");
+
+const routerCountries = express.Router();
+
+routerCountries.get("/", (req, res) => {
+    res.send(`All countries... path=${req.originalUrl}`);
+});
+
+routerCountries.get("/UY", (req, res) => {
+    res.send(`GET UY (Uruguay)... path=${req.originalUrl}`);
+});
+
+routerCountries.get("/:country", (req, res) => {
+    res.send(`GET Single country... ${req.params.country}`);
+});
+
+module.exports = routerCountries;
diff --git a/chapter04/src/router_home.js b/chapter04/src/router_home.js
new file mode 100644
index 0000000..6bbd777
--- /dev/null
+++ b/chapter04/src/router_home.js
@@ -0,0 +1,16 @@
+/* @flow */
+"use strict";
+
+const express = require("express");
+
+const routerHome = express.Router();
+
+const routerCountries = require("./router_countries.js");
+const routerRegions = require("./router_regions.js");
+const routerCities = require("./router_cities.js");
+
+routerHome.use("/countries", routerCountries);
+routerHome.use("/regions", routerRegions);
+routerHome.use("/cities", routerCities);
+
+module.exports = routerHome;
diff --git a/chapter04/src/router_regions.js b/chapter04/src/router_regions.js
new file mode 100644
index 0000000..a1ed456
--- /dev/null
+++ b/chapter04/src/router_regions.js
@@ -0,0 +1,32 @@
+/* @flow */
+"use strict";
+
+const express = require("express");
+
+const routerRegions = express.Router();
+
+routerRegions.get("/", (req, res) => {
+    res.send(`Region GET ALL... `);
+});
+
+routerRegions.get("/:country", (req, res) => {
+    res.send(`Region GET ALL FOR Country=${req.params.country}`);
+});
+
+routerRegions.get("/:country/:id", (req, res) => {
+    res.send(`Region GET ${req.params.country}/${req.params.id}`);
+});
+
+routerRegions.delete("/:country/:id", (req, res) => {
+    res.send(`Region DELETE... ${req.params.country}/${req.params.id}`);
+});
+
+routerRegions.post("/", (req, res) => {
+    res.send(`Region POST... `);
+});
+
+routerRegions.put("/:country/:id", (req, res) => {
+    res.send(`Region PUT... ${req.params.country}/${req.params.id}`);
+});
+
+module.exports = routerRegions;
diff --git a/chapter04/src/routing.js b/chapter04/src/routing.js
new file mode 100644
index 0000000..3997b31
--- /dev/null
+++ b/chapter04/src/routing.js
@@ -0,0 +1,19 @@
+/* @flow */
+"use strict";
+
+const express = require("express");
+const app = express();
+
+const myRouter = require("./router_home.js");
+
+app.use("/", myRouter);
+
+// eslint-disable-next-line no-unused-vars
+app.use((err, req, res, next) => {
+    console.error("Error....", err.message);
+    res.status(500).send("INTERNAL SERVER ERROR");
+});
+
+app.listen(8080, () =>
+    console.log("Routing ready at http://localhost:8080")
+);