diff --git a/datasette/app.py b/datasette/app.py
index b8e27f3c..321e4a92 100644
--- a/datasette/app.py
+++ b/datasette/app.py
@@ -1158,7 +1158,7 @@ class DatasetteRouter:
                 await template.render_async(
                     dict(
                         info,
-                        base_url=self.ds.config("base_url"),
+                        urls=self.ds.urls,
                         app_css_hash=self.ds.app_css_hash(),
                     )
                 ),
@@ -1270,19 +1270,26 @@ class Urls:
     def __init__(self, ds):
         self.ds = ds
 
+    def path(self, path):
+        if path.startswith("/"):
+            path = path[1:]
+        return self.ds.config("base_url") + path
+
     def instance(self):
-        return self.ds.config("base_url")
+        return self.path("")
 
     def static(self, path):
-        return "{}-/static/{}".format(self.instance(), path)
+        return self.path("-/static/{}".format(path))
+
+    def logout(self):
+        return self.path("-/logout")
 
     def database(self, database):
         db = self.ds.databases[database]
-        base_url = self.ds.config("base_url")
         if self.ds.config("hash_urls") and db.hash:
-            return "{}{}-{}".format(base_url, database, db.hash[:HASH_LENGTH])
+            return self.path("{}-{}".format(database, db.hash[:HASH_LENGTH]))
         else:
-            return "{}{}".format(base_url, database)
+            return self.path(database)
 
     def table(self, database, table):
         return "{}/{}".format(self.database(database), urllib.parse.quote_plus(table))
diff --git a/datasette/templates/allow_debug.html b/datasette/templates/allow_debug.html
index 8ec03a5a..0f1b30f0 100644
--- a/datasette/templates/allow_debug.html
+++ b/datasette/templates/allow_debug.html
@@ -35,7 +35,7 @@ p.message-warning {
 
 <p>Use this tool to try out different actor and allow combinations. See <a href="https://docs.datasette.io/en/stable/authentication.html#defining-permissions-with-allow-blocks">Defining permissions with "allow" blocks</a> for documentation.</p>
 
-<form action="/-/allow-debug" method="get">
+<form action="{{ urls.path('-/allow-debug') }}" method="get">
     <div class="two-col">
         <p><label>Allow block</label></p>
         <textarea name="allow">{{ allow_input }}</textarea>
diff --git a/datasette/templates/base.html b/datasette/templates/base.html
index fd4cf504..84708325 100644
--- a/datasette/templates/base.html
+++ b/datasette/templates/base.html
@@ -2,7 +2,7 @@
 <html>
 <head>
     <title>{% block title %}{% endblock %}</title>
-    <link rel="stylesheet" href="{{ base_url }}-/static/app.css?{{ app_css_hash }}">
+    <link rel="stylesheet" href="{{ urls.static('app.css') }}?{{ app_css_hash }}">
     <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
 {% for url in extra_css_urls %}
     <link rel="stylesheet" href="{{ url.url }}"{% if url.sri %} integrity="{{ url.sri }}" crossorigin="anonymous"{% endif %}>
@@ -18,7 +18,7 @@
     {% if actor %}
     <div class="logout">
         <strong>{{ display_actor(actor) }}</strong>{% if show_logout %} &middot;
-        <form action="/-/logout" method="post">
+        <form action="{{ urls.logout() }}" method="post">
             <input type="hidden" name="csrftoken" value="{{ csrftoken() }}">
             <button class="button-as-link">Log out</button>
         </form>{% endif %}
diff --git a/datasette/templates/error.html b/datasette/templates/error.html
index 46573f30..5c651d4e 100644
--- a/datasette/templates/error.html
+++ b/datasette/templates/error.html
@@ -4,7 +4,7 @@
 
 {% block nav %}
     <p class="crumbs">
-        <a href="/">home</a>
+        <a href="{{ urls.instance() }}">home</a>
     </p>
     {{ super() }}
 {% endblock %}
diff --git a/datasette/views/database.py b/datasette/views/database.py
index 772271c4..74509278 100644
--- a/datasette/views/database.py
+++ b/datasette/views/database.py
@@ -102,6 +102,7 @@ class DatabaseView(DataView):
         return (
             {
                 "database": database,
+                "path": self.ds.urls.database(database),
                 "size": db.size,
                 "tables": tables,
                 "hidden_count": len([t for t in tables if t["hidden"]]),
diff --git a/docs/internals.rst b/docs/internals.rst
index d02b4c67..95bdfc68 100644
--- a/docs/internals.rst
+++ b/docs/internals.rst
@@ -375,6 +375,14 @@ The ``datasette.urls`` object contains methods for building URLs to pages within
 ``datasette.urls.instance()``
     Returns the URL to the Datasette instance root page. This is usually ``"/"``
 
+``datasette.urls.path(path)``
+    Takes a path and returns the full path, taking ``base_url`` into account.
+
+    For example, ``datasette.urls.path("-/logout")`` will return the path to the logout page, which will be ``"/-/logout"`` by default or ``/prefix-path/-/logout`` if ``base_url`` is set to ``/prefix-path/``
+
+``datasette.urls.logout()``
+    Returns the URL to the logout page, usually ``"/-/logout"``.
+
 ``datasette.urls.database(database_name)``
     Returns the URL to a database page, for example ``"/fixtures"``
 
