This photo taken on April 2, 2026 shows the Bobolice Castle in Bobolice, Poland. Built in the 14th century, the castle is one of the best-preserved medieval castles along the Trail of the Eagles' Nests. The Trail of the Eagles' Nests is a renowned historical and cultural tourism route in southern Poland. Connecting southern Polish cities of Krakow and Czestochowa, the route stretches about 160 km and features more than 20 medieval castles built on limestone cliffs. (Photo by Aleksy Witwicki/Xinhua)

(260403) -- OGRODZIENIEC, April 3, 2026 (Xinhua) -- This photo taken on April 2, 2026 shows the ruins of the Ogrodzieniec Castle in Podzamcze, Poland. Built in the 14th century, the castle is one of the most prominent medieval strongholds along the Trail of the Eagles' Nests. The Trail of the Eagles' Nests is a renowned historical and cultural tourism route in southern Poland. Connecting southern Polish cities of Krakow and Czestochowa, the route stretches about 160 km and features more than 20 medieval castles built on limestone cliffs. (Photo by Aleksy Witwicki/Xinhua)

(260403) -- MIROW, April 3, 2026 (Xinhua) -- An aerial drone photo taken on April 2, 2026 shows the Mirow Castle in Mirow, Poland. Built in the mid-14th century, the castle is one of the medieval strongholds along the Trail of the Eagles' Nests. The Trail of the Eagles' Nests is a renowned historical and cultural tourism route in southern Poland. Connecting southern Polish cities of Krakow and Czestochowa, the route stretches about 160 km and features more than 20 medieval castles built on limestone cliffs. (Photo by Aleksy Witwicki/Xinhua)

(260403) -- OGRODZIENIEC, April 3, 2026 (Xinhua) -- This photo taken on April 2, 2026 shows an interior of the ruins of the Ogrodzieniec Castle in Podzamcze, Poland. Built in the 14th century, the castle is one of the most prominent medieval strongholds along the Trail of the Eagles' Nests. The Trail of the Eagles' Nests is a renowned historical and cultural tourism route in southern Poland. Connecting southern Polish cities of Krakow and Czestochowa, the route stretches about 160 km and features more than 20 medieval castles built on limestone cliffs. (Photo by Aleksy Witwicki/Xinhua)

(260403) -- OGRODZIENIEC, April 3, 2026 (Xinhua) -- This photo taken on April 2, 2026 shows an interior of the ruins of the Ogrodzieniec Castle in Podzamcze, Poland. Built in the 14th century, the castle is one of the most prominent medieval strongholds along the Trail of the Eagles' Nests. The Trail of the Eagles' Nests is a renowned historical and cultural tourism route in southern Poland. Connecting southern Polish cities of Krakow and Czestochowa, the route stretches about 160 km and features more than 20 medieval castles built on limestone cliffs. (Photo by Aleksy Witwicki/Xinhua)

(260403) -- OGRODZIENIEC, April 3, 2026 (Xinhua) -- This photo taken on April 2, 2026 shows the ruins of the Ogrodzieniec Castle in Podzamcze, Poland. Built in the 14th century, the castle is one of the most prominent medieval strongholds along the Trail of the Eagles' Nests. The Trail of the Eagles' Nests is a renowned historical and cultural tourism route in southern Poland. Connecting southern Polish cities of Krakow and Czestochowa, the route stretches about 160 km and features more than 20 medieval castles built on limestone cliffs. (Photo by Aleksy Witwicki/Xinhua)

(260403) -- OGRODZIENIEC, April 3, 2026 (Xinhua) -- This photo taken on April 2, 2026 shows the ruins of the Ogrodzieniec Castle in Podzamcze, Poland. Built in the 14th century, the castle is one of the most prominent medieval strongholds along the Trail of the Eagles' Nests. The Trail of the Eagles' Nests is a renowned historical and cultural tourism route in southern Poland. Connecting southern Polish cities of Krakow and Czestochowa, the route stretches about 160 km and features more than 20 medieval castles built on limestone cliffs. (Photo by Aleksy Witwicki/Xinhua)

An aerial drone photo taken on April 2, 2026 shows the Bobolice Castle in Bobolice, Poland. Built in the 14th century, the castle is one of the best-preserved medieval castles along the Trail of the Eagles' Nests. The Trail of the Eagles' Nests is a renowned historical and cultural tourism route in southern Poland. Connecting southern Polish cities of Krakow and Czestochowa, the route stretches about 160 km and features more than 20 medieval castles built on limestone cliffs. (Photo by Aleksy Witwicki/Xinhua)

This photo taken on April 2, 2026 shows a rural yard with the Bobolice Castle in the background in Bobolice, Poland. Built in the 14th century, the castle is one of the best-preserved medieval castles along the Trail of the Eagles' Nests. The Trail of the Eagles' Nests is a renowned historical and cultural tourism route in southern Poland. Connecting southern Polish cities of Krakow and Czestochowa, the route stretches about 160 km and features more than 20 medieval castles built on limestone cliffs. (Photo by Aleksy Witwicki/Xinhua)

(260403) -- MIROW, April 3, 2026 (Xinhua) -- This photo taken on April 2, 2026 shows the Mirow Castle and nearby residential houses in Mirow, Poland. Built in the mid-14th century, the castle is one of the medieval strongholds along the Trail of the Eagles' Nests. The Trail of the Eagles' Nests is a renowned historical and cultural tourism route in southern Poland. Connecting southern Polish cities of Krakow and Czestochowa, the route stretches about 160 km and features more than 20 medieval castles built on limestone cliffs. (Photo by Aleksy Witwicki/Xinhua)

(260403) -- MIROW, April 3, 2026 (Xinhua) -- An aerial drone photo taken on April 2, 2026 shows the Mirow Castle in Mirow, Poland. Built in the mid-14th century, the castle is one of the medieval strongholds along the Trail of the Eagles' Nests. The Trail of the Eagles' Nests is a renowned historical and cultural tourism route in southern Poland. Connecting southern Polish cities of Krakow and Czestochowa, the route stretches about 160 km and features more than 20 medieval castles built on limestone cliffs. (Photo by Aleksy Witwicki/Xinhua)