diff --git a/core/includes/batch.inc b/core/includes/batch.inc
index b9e49f7..0e9dfe1 100644
--- a/core/includes/batch.inc
+++ b/core/includes/batch.inc
@@ -452,7 +452,8 @@ function _batch_finished() {
     if ($_batch['form_state']->getRedirect() === NULL) {
       $redirect = $_batch['batch_redirect'] ?: $_batch['source_url'];
       $options = UrlHelper::parse($redirect);
-      if (UrlHelper::isExternal($options['path']) || strpos($options['path'], 'base://') === 0) {
+      // Any path with a scheme does not correspond to a route.
+      if (parse_url($options['path'], PHP_URL_SCHEME)) {
         $redirect = Url::unrouted($options['path'], $options);
       }
       else {
diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 2fc2d56..d763045 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -543,7 +543,7 @@ function install_run_task($task, &$install_state) {
       }
       // Process the batch. For progressive batches, this will redirect.
       // Otherwise, the batch will complete.
-      $response = batch_process('base://' . install_redirect_url($install_state), install_full_redirect_url($install_state));
+      $response = batch_process(preg_replace('@^core/@', 'base://', install_redirect_url($install_state)), install_full_redirect_url($install_state));
       if ($response instanceof Response) {
         // Save $_SESSION data from batch.
         \Drupal::service('session_manager')->save();
diff --git a/core/lib/Drupal/Core/Menu/MenuLinkBase.php b/core/lib/Drupal/Core/Menu/MenuLinkBase.php
index 6edbcc0..c0f05e0 100644
--- a/core/lib/Drupal/Core/Menu/MenuLinkBase.php
+++ b/core/lib/Drupal/Core/Menu/MenuLinkBase.php
@@ -141,8 +141,7 @@ public function getUrlObject($title_attribute = TRUE) {
       return new Url($this->pluginDefinition['route_name'], $this->pluginDefinition['route_parameters'], $options);
     }
     else {
-      $url = Url::unrouted($this->pluginDefinition['url'], $options);
-      return $url;
+      return Url::unrouted($this->pluginDefinition['url'], $options);;
     }
   }
 
diff --git a/core/lib/Drupal/Core/Url.php b/core/lib/Drupal/Core/Url.php
index bdae691..04a961c 100644
--- a/core/lib/Drupal/Core/Url.php
+++ b/core/lib/Drupal/Core/Url.php
@@ -254,7 +254,7 @@ public function isRouted() {
    * @return string
    *
    * @throws \UnexpectedValueException.
-   *   If this is an URI with no corresponding route.
+   *   If this is a URI with no corresponding route.
    */
   public function getRouteName() {
     if ($this->unrouted) {
@@ -270,7 +270,7 @@ public function getRouteName() {
    * @return array
    *
    * @throws \UnexpectedValueException.
-   *   If this is an URI with no corresponding route.
+   *   If this is a URI with no corresponding route.
    */
   public function getRouteParameters() {
     if ($this->unrouted) {
@@ -289,7 +289,7 @@ public function getRouteParameters() {
    * @return $this
    *
    * @throws \UnexpectedValueException.
-   *   If this is an URI with no corresponding route.
+   *   If this is a URI with no corresponding route.
    */
   public function setRouteParameters($parameters) {
     if ($this->unrouted) {
@@ -310,7 +310,7 @@ public function setRouteParameters($parameters) {
    * @return $this
    *
    * @throws \UnexpectedValueException.
-   *   If this is an URI with no corresponding route.
+   *   If this is a URI with no corresponding route.
    */
   public function setRouteParameter($key, $value) {
     if ($this->unrouted) {
@@ -471,7 +471,7 @@ public function toRenderArray() {
    *   The internal path for this route.
    *
    * @throws \UnexpectedValueException.
-   *   If this is an URI with no corresponding system path.
+   *   If this is a URI with no corresponding system path.
    *
    * @deprecated in Drupal 8.x-dev, will be removed before Drupal 8.0.
    *   System paths should not be used - use route names and parameters.
diff --git a/core/lib/Drupal/Core/Utility/UnroutedUrlAssemblerInterface.php b/core/lib/Drupal/Core/Utility/UnroutedUrlAssemblerInterface.php
index cba87fe..36fca11 100644
--- a/core/lib/Drupal/Core/Utility/UnroutedUrlAssemblerInterface.php
+++ b/core/lib/Drupal/Core/Utility/UnroutedUrlAssemblerInterface.php
@@ -12,23 +12,24 @@
 interface UnroutedUrlAssemblerInterface {
 
   /**
-   * Builds a domain-local or external URL from a path or URL.
+   * Builds a domain-local or external URL from a URI.
    *
    * For actual implementations the logic probably has to be split up between
-   * domain-local and external URLs.
+   * domain-local URIs and external URLs.
    *
    * @param string $uri
-   *   A path on the same domain or external URL being linked to, such as "foo"
+   *   A local URI or an external URL being linked to, such as "base://foo"
    *    or "http://example.com/foo".
    *   - If you provide a full URL, it will be considered an external URL as
    *     long as it has an allowed protocol.
-   *   - If you provide only a path (e.g. "foo"), it will be
-   *     considered a URL local to the same domain. Additional query
-   *     arguments for local paths must be supplied in $options['query'], not
-   *     included in $path.
+   *   - If you provide only a local URI (e.g. "base://foo"), it will be
+   *     considered a path local to Drupal, but not handled by the routing
+   *     system.  The base path (the subdirectory where the front controller
+   *     is found) will be added to the path. Additional query arguments for
+   *     local paths must be supplied in $options['query'], not part of $uri.
    *   - If your external URL contains a query (e.g. http://example.com/foo?a=b),
    *     then you can either URL encode the query keys and values yourself and
-   *     include them in $path, or use $options['query'] to let this method
+   *     include them in $uri, or use $options['query'] to let this method
    *     URL encode them.
    *
    * @param array $options
diff --git a/core/modules/link/src/Plugin/Field/FieldFormatter/LinkFormatter.php b/core/modules/link/src/Plugin/Field/FieldFormatter/LinkFormatter.php
index 65e37bf..2d9cc98 100644
--- a/core/modules/link/src/Plugin/Field/FieldFormatter/LinkFormatter.php
+++ b/core/modules/link/src/Plugin/Field/FieldFormatter/LinkFormatter.php
@@ -207,22 +207,7 @@ protected function buildUrl(LinkItemInterface $item) {
     }
 
     if ($item->isExternal()) {
-      // @todo LinkItemInterface shouldn't treat items with no scheme as
-      //   external, including <front>. All the code here should be removed
-      //   except the first case where we have a valid scheme.  There needs to
-      //   be some fixes in RDF module since changing this causes failures in
-      //   Drupal\rdf\Tests\Field\LinkFieldRdfaTest
-      //   https://www.drupal.org/node/2346645
-      if (parse_url($item->url, PHP_URL_SCHEME)) {
-        $url = Url::unrouted($item->url, $options);
-      }
-      elseif ($item->url == '<front>') {
-        $url = new Url('<front>');
-      }
-      else {
-        // No base path - assume internal.
-        $url = Url::createFromRequest(Request::create('/' . ltrim($item->url, '/')));
-      }
+      $url = Url::unrouted($item->url, $options);
     }
     else {
       $url = Url::routed($item->route_name, (array) $item->route_parameters, (array) $options);
diff --git a/core/modules/rdf/src/Tests/Field/LinkFieldRdfaTest.php b/core/modules/rdf/src/Tests/Field/LinkFieldRdfaTest.php
index 8c23c07..8478bae 100644
--- a/core/modules/rdf/src/Tests/Field/LinkFieldRdfaTest.php
+++ b/core/modules/rdf/src/Tests/Field/LinkFieldRdfaTest.php
@@ -75,7 +75,8 @@ public function testAllFormattersInternal() {
     // Set up test values.
     $this->testValue = 'admin';
     $this->entity = entity_create('entity_test', array());
-    $this->entity->{$this->fieldName}->url = $this->testValue;
+    $this->entity->{$this->fieldName}->route_name = 'system.admin';
+    $this->entity->{$this->fieldName}->url = 'admin';
 
     // Set up the expected result.
     // AssertFormatterRdfa looks for a full path.
@@ -94,7 +95,8 @@ public function testAllFormattersFront() {
     // Set up test values.
     $this->testValue = '<front>';
     $this->entity = entity_create('entity_test', array());
-    $this->entity->{$this->fieldName}->url = $this->testValue;
+    $this->entity->{$this->fieldName}->route_name = $this->testValue;
+    $this->entity->{$this->fieldName}->url = '<front>';
 
     // Set up the expected result.
     $expected_rdf = array(
diff --git a/core/modules/shortcut/src/Entity/Shortcut.php b/core/modules/shortcut/src/Entity/Shortcut.php
index 4c331f7..4bd041e 100644
--- a/core/modules/shortcut/src/Entity/Shortcut.php
+++ b/core/modules/shortcut/src/Entity/Shortcut.php
@@ -135,6 +135,9 @@ public static function preCreate(EntityStorageInterface $storage, array &$values
   public function preSave(EntityStorageInterface $storage) {
     parent::preSave($storage);
 
+    // @todo fix PathValidatorInterface::getUrlIfValid() so we can use it
+    //   here. The problem is that we need an exception, not a FALSE
+    //   return value. https://www.drupal.org/node/2346695
     if ($this->path->value == '<front>') {
       $url = new Url($this->path->value);
     }
diff --git a/core/modules/update/update.report.inc b/core/modules/update/update.report.inc
index e885ce5..b5215e2 100644
--- a/core/modules/update/update.report.inc
+++ b/core/modules/update/update.report.inc
@@ -6,6 +6,7 @@
  */
 
 use Drupal\Core\Template\Attribute;
+use Drupal\Core\Url;
 
 /**
  * Prepares variables for project status report templates.
@@ -135,7 +136,7 @@ function template_preprocess_update_project_status(&$variables) {
 
   // Set the project title and URL.
   $variables['title'] = (isset($project['title'])) ? $project['title'] : $project['name'];
-  $variables['url'] = (isset($project['link'])) ? \Drupal::service('unrouted_url_assembler')->assemble($project['link']) : NULL;
+  $variables['url'] = (isset($project['link'])) ? Url::unrouted($project['link'])->toString() : NULL;
 
   $variables['install_type'] = $project['install_type'];
   if ($project['install_type'] == 'dev' && !empty($project['datestamp'])) {
diff --git a/core/tests/Drupal/Tests/Core/UnroutedUrlTest.php b/core/tests/Drupal/Tests/Core/ExternalUrlTest.php
similarity index 100%
rename from core/tests/Drupal/Tests/Core/UnroutedUrlTest.php
rename to core/tests/Drupal/Tests/Core/ExternalUrlTest.php