You can try the next European Heritage Days in September and visit monuments and sites that are usually closed for free or at a reduced rate!
How does it work?
For one weekend every September, the 50 countries that signed the European Cultural Convention organize cultural events to highlight local skills and traditions, architecture and works of art. Every year the events have a special theme that varies in each country. It can be specific periods in history or specific forms of heritage.
Since 1999, the European Heritage Days have had the slogan: "Europe, a common heritage". Cultural heritage brings Europeans together, whatever their cultural, linguistic or religious backgrounds. As a joint action of the Council of Europe and the European Commission, the European Heritage Days aim to raise European citizens’ awareness of the richness and cultural diversity of Europe; as well as to counter racism and xenophobia and to encourage greater tolerance in Europe and beyond.