The Schengen Area is founded on the principles of respect for fundamental human dignity, freedom, democracy, equality, the rule of law, and the protection of human rights. Presently, it stands as the largest area facilitating the free movement of people. Its most distinguishing feature is the absence of internal borders, a testament to the unity achieved among member states. This unity extends to collaborative efforts aimed at thwarting both external and internal threats, thus safeguarding the continued existence of the Schengen Area. In the past decade, Schengen member countries have encountered various threats that have shaken the very foundations of the Schengen Area. Events such as the European migrant crisis in 2015, the COVID-19 pandemic, and the conflict in Ukraine have led to the temporary closure of internal borders within the Schengen Area. These challenges have at times prompted member states to take actions that may appear inconsistent with the fundamental principles of the Schengen Acquis. The objective of this master's thesis is to investigate whether the current Schengen Area model remains sustainable, particularly in the context of potential future enlargements. It seeks to explore whether the European Union and its member states can ensure the security and well-being of European Union citizens while upholding the principles and values that underpin the Schengen Area. The Master's thesis identifies the foundational values upon which the Schengen Area was established and highlights the significant challenges that member states confronted within a relatively brief timeframe, particularly concerning the integration of new member states into the Schengen Area. Over the years, the European Union and its member states have made concerted efforts to respond to these challenges. While they have effectively overcome crises, it has become increasingly apparent that enhanced cooperation and improved organization at the collective level of all member countries are imperative for the sustainable preservation of security within the Schengen Area and the facilitation of its expansion.