The tower gives a compact overview of central Reykjavík rather than a wilderness panorama.
The church describes the tower as 73 metres high. The nave is wheelchair accessible, and an elevator reaches the eighth floor; the open-air platform on the ninth floor requires a short staircase. A quick exterior and nave visit can take 20 to 30 minutes, while the tower, a queue, or time spent listening to the organ can extend the stop toward an hour.
On a clear day you can read the city's colorful roofs, harbor edge, surrounding hills, and the compact street grid below. It is useful early in a Reykjavík stay, but it is not essential to understanding the church. In low cloud or poor visibility, spend the time on the facade, nave, and surrounding streets instead.
For a broader indoor attraction and a different hilltop view, compare it with Perlan. Hallgrímskirkja is the better fit for a central walking day; Perlan asks for more time and has its own exhibitions and setting.