"I've absolutely loved it. It has been my life really."
She said her favourite exhibition during the past couple of decades had to be the Maori battalion exhibition in 2000.
"It was really tough to do because you are dealing with death and people's emotion," she said.
"Chris Currie and I, and others, worked on it and it was as good as anything anywhere, but it was just the heart of it that was really special."
She said another stand-out exhibition she worked on was Daughter of the Land in 1993, looking at the role of Maori and European women winning the right to vote.
Ms Somerville has held the role of Rotorua Museum volunteer guide co-ordinator for a number of years now, training museum tour guides.
She said she loved the role and was proud of the work all 80 volunteer guides did in Rotorua.
Two years before starting work at the museum, Ms Somerville began an art column in the Rotorua Daily Post which she continued for 18 years.
"One of the reasons I got the job was because I was writing an art column for The Daily Post," she said with a laugh.
When she started at the museum in 1990 there were only five staff.
Now there are almost 20 staff and 100,000 visitors a year. She said that was a major reason for leaving the museum, knowing it was in good hands. Her plan now was to take some time off work.
Her final day at the museum is tomorrow.