The back dresser in the master bedroom has a hidden panel that leads to the hidden treasury.
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 mod supported items such as More Interesting Loot 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 immediately into the treasury.