diff --git a/CMakeLists.txt b/CMakeLists.txt
index f0130a9..b14a724 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -6,7 +6,7 @@
 # v. 2.0. If a copy of the MPL was not distributed with this file, You can
 # obtain one at http://mozilla.org/MPL/2.0/.
 
-cmake_minimum_required(VERSION 3.18)
+cmake_minimum_required(VERSION 3.21)
 
 project("covfie" VERSION 0.10.0)
 
@@ -41,16 +41,37 @@ add_subdirectory(lib)
 
 # The benchmarks should be build only if requested...
 if(COVFIE_BUILD_BENCHMARKS)
+    if(NOT PROJECT_IS_TOP_LEVEL)
+        message(
+            FATAL_ERROR
+            "Build of benchmarks was requested, but covfie is not the top level project."
+        )
+    endif()
+
     add_subdirectory(benchmarks)
 endif()
 
 # ...the same goes for the tests...
 if(COVFIE_BUILD_TESTS)
+    if(NOT PROJECT_IS_TOP_LEVEL)
+        message(
+            FATAL_ERROR
+            "Build of tests was requested, but covfie is not the top level project."
+        )
+    endif()
+
     add_subdirectory(tests)
 endif()
 
 # ...and the examples.
 if(COVFIE_BUILD_EXAMPLES)
+    if(NOT PROJECT_IS_TOP_LEVEL)
+        message(
+            FATAL_ERROR
+            "Build of examples was requested, but covfie is not the top level project."
+        )
+    endif()
+
     add_subdirectory(examples)
 endif()
 
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 1aec043..e1de7f3 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -8,20 +8,7 @@
 
 # All the tests here will require Google Test, so we will go ahead and set it
 # up.
-# Set up GoogleTest.
-option(COVFIE_SETUP_GOOGLETEST "Set up the GoogleTest targets explicitly" TRUE)
-option(
-    COVFIE_USE_SYSTEM_GOOGLETEST
-    "Pick up an existing installation of GoogleTest from the build environment"
-    TRUE
-)
-if(COVFIE_SETUP_GOOGLETEST)
-    if(COVFIE_USE_SYSTEM_GOOGLETEST)
-        find_package(GTest CONFIG REQUIRED)
-    else()
-        add_subdirectory(googletest)
-    endif()
-endif()
+find_package(GTest CONFIG REQUIRED)
 
 # Set up the C++ compiler flags for the tests.
 include(covfie-compiler-options-cpp)
diff --git a/tests/googletest/CMakeLists.txt b/tests/googletest/CMakeLists.txt
deleted file mode 100644
index 413f046..0000000
--- a/tests/googletest/CMakeLists.txt
+++ /dev/null
@@ -1,54 +0,0 @@
-# This file is part of covfie, a part of the ACTS project
-#
-# Copyright (c) 2022 CERN
-#
-# This Source Code Form is subject to the terms of the Mozilla Public License,
-# v. 2.0. If a copy of the MPL was not distributed with this file, You can
-# obtain one at http://mozilla.org/MPL/2.0/.
-
-# CMake include(s).
-cmake_minimum_required(VERSION 3.11)
-include(FetchContent)
-
-# Silence FetchContent warnings with CMake >=3.24.
-if(POLICY CMP0135)
-    cmake_policy(SET CMP0135 NEW)
-endif()
-
-# Tell the user what's happening.
-message(STATUS "Building GoogleTest as part of the Covfie project")
-
-# Declare where to get GoogleTest from.
-FetchContent_Declare(
-    GoogleTest
-    URL
-        "https://github.com/google/googletest/archive/refs/tags/v1.14.0.tar.gz"
-    URL_MD5 "c8340a482851ef6a3fe618a082304cfc"
-)
-
-# Options used in the build of GoogleTest.
-set(BUILD_GMOCK FALSE CACHE BOOL "Turn off the build of GMock")
-set(INSTALL_GTEST FALSE CACHE BOOL "Turn off the installation of GoogleTest")
-if(WIN32)
-    set(gtest_force_shared_crt
-        TRUE
-        CACHE BOOL
-        "Use shared (DLL) run-time library, even with static libraries"
-    )
-endif()
-
-# Silence some warnings with modern versions of CMake on macOS.
-set(CMAKE_MACOSX_RPATH TRUE)
-
-# Get it into the current directory.
-FetchContent_Populate(GoogleTest)
-add_subdirectory(
-    "${googletest_SOURCE_DIR}"
-    "${googletest_BINARY_DIR}"
-    EXCLUDE_FROM_ALL
-)
-
-# Set up aliases for the GTest targets with the same name that they have
-# when we find GTest pre-installed.
-add_library(GTest::gtest ALIAS gtest)
-add_library(GTest::gtest_main ALIAS gtest_main)
diff --git a/tests/googletest/README.md b/tests/googletest/README.md
deleted file mode 100644
index 87c642c..0000000
--- a/tests/googletest/README.md
+++ /dev/null
@@ -1,10 +0,0 @@
-# GoogleTest Build Instructions
-
-This subdirectory holds instructions for building
-[GoogleTest](https://github.com/google/googletest) as part of this project.
-This is meant to come in handy for building the project's tests in environments
-which do not provide GoogleTest themselves.
-
-Note that since GoogleTest is only needed for the unit tests of this project,
-which are not installed together with the project, GoogleTest is not installed
-together with the project either.