Colo. Rev. Stat. § 3-1-105
Exclusive jurisdiction for all purposes, except such as are in this section and section 3-1-107 expressly reserved, over all that tract, piece, or parcel of land situate, lying, and being in the city and county of Denver, in the state of Colorado, known and distinguished as and being lots numbered one, two, three, four, five, six, seven, eight, in block ninety-eight, in the east division of the city and county of Denver, bounded on the northwest by Arapahoe street, on the northeast by Sixteenth street, on the southeast by an alley running from Fifteenth street to Sixteenth street, between Arapahoe and Curtis streets, and on the southwest by the line dividing said lot eight from lot nine in said block, be and hereby is ceded, granted, transferred, conferred, and confirmed unto the United States of America, as a proper site for the erection thereon of a suitable building for the accommodation of the United States district and circuit courts and other government offices, in the manner and form in this section and section 3-1-107 prescribed, from and after the time when the United States shall become the owner of said tract, and for and during the time the United States shall remain the owner thereof; but, nevertheless, jurisdiction to serve the civil process of state, county, and municipal courts and tribunals within said tract, and also to serve and execute thereon, process in criminal cases by state, county, and municipal officers, in respect of offenses, misdemeanors, crimes, and felonies committed outside of said tract is reserved to the state of Colorado.
C.R.S. § 3-1-105