For a more in-depth look at Gustav Vigeland's work, this museum is just opposite the southern entrance to Frognerparken. It was built by the city in the 1920s as a home and studio for the sculptor in exchange for the donation of a significant proportion of his life's work. It contains his early collection of statuary and monuments to public figures, as well as plaster moulds, woodblock prints and sketches.
When he died in 1943, Vigeland's ashes were deposited in the tower and the museum was opened to the public four years later. Guided tours are available (in English), with prior notice, from 1000kr per group; sketching (pencil only) is encouraged and you can borrow sketching boards and folding chairs. In addition to the works of Vigeland, the museum also has a very good program of seasonal contemporary shows.