The new repository will hold the collections of the National Art Museum (LNMM), the National History Museum, the Literature and Music Museum and the Rīga Film Museum.
"We are storing not our private property, but the common property of the whole society.
It's our common concern that these values are stored as they need to," LNMM director Māra Lāce told Latvian Radio Tuesday.
Currently the collections of these museums are stored in unfavorable conditions.
For example, about 28,000 units of the LNMM collection on modern art is stored at the Arsenāls gallery, originally a 19th-century customs storehouse, where the lack of space harms the artworks and hinders researchers' attempts to work with them.
"Moisture from the outside affects the works here, too," said LNMM representative Ilze Putniņa.
While other museums are storing collections in similarly unsuitable places.
After the 2013 fire at the Rīga Castle, the National History Museum is storing its valuables at a former vocational school near the Salu Bridge.
While the collection of the Rīga Film Museum rests in three cramped rooms by the Theater Museum on Smiļģa street.
The Literature and Music Museum is to move its collection to the new repository complex too. The museum currently resides in temporary premises on Tērbatas street.
The complex was designed by Arhitektu birojs Krasts, while construction will be undertaken by Re&Re.
Construction is estimated to cost €20.5m. The grand repository should be finished in spring 2018, just in time for Latvia's centenary.
However it will take about a year more to move the hundreds of thousands of valuables to the new storage place.