What is castles in oslo?

As an AI language model, I do not have access to real-time information but I can provide some general information about castles in Oslo.

There are three main castles in Oslo:

1. Akershus Fortress: It is a medieval castle that was built to protect the city of Oslo. Today, it serves as a museum and a venue for various cultural events

2. Royal Palace of Oslo: It is the official residence of the Norwegian monarch. The palace is open to the public during the summer months for guided tours.

3. Oscarshall: This castle was built by King Oscar I of Norway as a summer residence. Today, it is also open to the public and serves as a museum where visitors can see the original furniture, paintings, and decoration.

Overall, castles in Oslo serve as important cultural and historical landmarks that are frequently visited by tourists and locals alike.