Ecopetrol's recent Gibraltar discovery was made in a previously little known area of the northern Llanos foothills of the Eastern Cordillera of Colombia. The structure at Gibraltar is complex and comprises a thrust stack with which are associated hangingwall anticlines providing four-way closures (or three-way against a sealing fault). The Gibraltar-I well was originally drilled by Occidental in 2002. According to Ecopetrol's subsequent structural reinterpretation, this well penetrated the back limb of a fault propagation fold. This structural model was confirmed with a sidetrack well which penetrated the Palaeocene Barco Formation and demonstrated the presence of light hydrocarbons. A second objective of well re-entry at Gibraltar was to investigate the Eocene Mirador Formation, a major reservoir unit elsewhere in the Llanos foothills, in case of missed or bypassed pay. Tests of the Mirador Formation verified the presence of high quality 57° API degree condensate that flowed at a rate of 690 barrels per day together with 44 million cubic feet of rich gas per day. The success at Gibraltar will hopefully encourage further exploration developments in this remote and structurally-complex region.