The back dresser in the master bedroom has a hidden panel that leads to the hidden treasury.
|Version 5 Spoiler|
|The treasury can be located by activating a switch hidden behind a tapestry, above the desk in the master bedroom.|
The treasury can store septims and will dynamically display your wealth up to a value of 2 million. Items such as gold ingots, silver ingots, gems, and a number of mods' supported items such as More Interesting Loot (More Interesting Loot is not available for SSE) treasure will be counted in the display.
Additionally, there is an alternative display for King Orgnum's Coffer. When the Coffer is placed onto its pedestal here, it will yield a random amount of gold daily into the treasury.