Citation Excel (C560XL)
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 134; Flight Crew Total 5000; Flight Crew Type 452
Situational Awareness; Communication Breakdown
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action; Flight Crew Became Reoriented
Human Factors
I was piloting a Cessna Citation in the south part of ZZZ1 Class B airspace.  I was on an IFR flight plan and was in communication with Approach Control. From somewhere a few miles west of ZZZ2; I was told to turn to a heading of north and descend to 2;500'. After a short amount of time; I started to look at my charts thinking that was too low for my position. I recall the controller being busy; trying to reach an aircraft that did not respond; and was awaiting an opportunity to confirm my altitude; when the controller called my tail number and told me to immediately climb to 3500' as I was in the middle of antennas. I later listened to the tape; and ATC assigned us to 3;500'; but I understood 2;500'; and repeated back 2;500' twice.  Despite saying 2;500' twice; the controller did not catch it.
CE560 pilot reported receiving a low altitude alert from ATC when he misunderstood a clearance and descended 1000' lower than cleared.