In Haltia there's also interesting temporary exhibitions indoors:
The years in Perukka (Vuodet Perukassa) by Katja Ronkainen 4.2.-15.3.2020. Read more in Finnish
Best of "Nature picture of the year 2016-2018"
Come to Finland -posters from the 1900s
A textile work of Forest nature diversity, made by students at Omnia. Read more in Finnish
Archive of the previous Temporary exhibitions (with information in English):