Well, its semi-official, downtown adjacent Golden Triangle neighborhood is the most expensive neighborhood on average for a one-bedroom rental with a median (half were higher, half were lower) of $2,275/month in October 2015 according to San Francisco based Zumper, an apartment rental search and application app.
What is interesting is this is a neighborhood which has transformed immensely over the past two decades. While always home to the Denver Art Museum on the south-side of Civic Center (and of course the Burnham Hoyt/Michael Graves Denver Public Library), the area boomed when luxury condos were built between Lincoln Street and Speer Boulevard from 7th Avenue to 14th Avenue. In addition, the area welcomes the Clyfford Still Museum, a few unique mixed use projects and of course a central location.
Yet historically the mid-rises east of Lincoln Street have historically offered affordable rentals north and west of the Governors Park neighborhood as well as across Cherry Creek at Parkway Center.
If you have driven northbound on Speer Boulevard you will see new luxury rentals sprouting up along this historic street. At the intersection of 6th/Speer what was once a large gas station has given way to a mid-rise new development as has a lot to the northwest beyond Broadway.
For additional details, here is a link to the article in the Denver Business Journal