Akershus Castle and Fortress is a medieval complex that was built to protect Oslo. It has also been used as a prison. The main building is now used for official events and dinners for the foreign heads of state. Akershus fortress is still a military area but is open to the public daily until 21:00. In addition to the castle, the Norwegian Armed Forces Museum and Norway's Resistance Museum can be visited there. Norwegian Royalty has been buried in the Royal Mausoleum in the castle. His Majesty the Kings Guard is responsible for guarding the fortress, with stationary guard posts during open hours, and patrols at night time. One of the stationary postings at the entrance is a popular photography spot for tourists visiting the fortress.

The Royal Palace was constructed for the new French-born king of unified Norway and Sweden. It has been the official royal residence since then. The palace is open for visitors with the advance appointment late June to mid-August. The beautiful baroque park of the palace is open for visitors every day.

Oslo Cathedral is an ancient church, dating to the 17th century. The Norwegian Royal Family and the Norwegian Government use the Cathedral for public events. In 2001, Oslo Cathedral was the site of the wedding of Haakon, Crown Prince of Norway, and Mette-Marit Tjessem Høiby. 

Oslo fjord is not a fjord in the geological sense - in Norwegian, the term fjord can refer to a wide range of waterways. It is an inlet in the south-east of Norway, stretching from an imaginary line between the Torbjørnskjær and Færder lighthouses and down to Langesund in the south to Oslo in the north. In the summer there are boats of all sizes on the fjord, and it is possible to go kayaking, canoeing, fishing, and sailing.

Opera house is a beautiful white structure, located by the water in Oslo harbor. It is the home of The Norwegian National Opera and Ballet, and the national opera theatre. The roof of the building angles to ground level, creating a large plaza that invites pedestrians to walk up and enjoy the panoramic views of Oslo. 

Holmenkollbakken is a large ski jumping hill located at Holmenkollen. It's a large hill with the capacity for 70,000 spectators, requiring the special permit for athletes to use. Holmenkollen has hosted the Holmenkollen Ski Festival since 1892. It's also a cross-country and biathlon venue. Holmenkollbakken is co-located with the Holmenkollen Ski Museum, which presents the history of skiing. It has a simulator that allows the public to visualize a ski jump in the hill.