"Ol' Blue Eyes" built the isolated mountain retreat high above the Palm Desert back in 1970 as an ideal getaway, and the 7.5-acre secluded compound features an abundance of space and luxury.

Dubbed the "Villa Maggio" -- named for the character that earned him an Oscar in "From Here to Eternity" -- the property was a personal residence for Sinatra for many years ... and provided a spot to escape, relax and party with friends and family.

The main house has 5 beds and 5.5 baths, but there's also a 3-bedroom guest house ... and a 1-bed pool house to go with the resort-style pool.

Though it's been recently renovated, Frank's home still has the tiles and wallpaper he chose in many places -- and all restoration's aimed to keep the home as close as possible to the original.

Of course, it's got panoramic mountain and valley views and parking for a few dozen cars -- but the real baller feature is ... the helipad!!! Screw that commuter traffic.

It's almost as if Sinatra had this place in mind when he sang his 1958 hit, "Let's Get Away from It All."