Syrian President Bashar al-Assad performed prayers on Friday for Islam's Eid al-Adha festival in the town of Qara, near an enclave surrendered on Monday by ISIS.
Confined to Damascus for long periods in the early part of Syria's six-year civil war, Assad has grown more confident in travelling around government-held areas as the army and its allies have won a series of victories.
The departure of ISIS and other groups from the Western Qalamoun district means the border with Lebanon is Syria's first to be controlled entirely by its army since early in the conflict.
The ISIS fighters who evacuated the district remained stuck in a convoy on Friday, two days after US-led coalition against the jihadists used air strikes to block it from crossing into their main territory in eastern Syria.
Qara is only a few miles from the pale, dry mountains delineating the frontier with Lebanon, straddling which ISIS and other militant groups held territory until August.
The ISIS fighters in the border pocket accepted a truce and evacuation deal after simultaneous but separate offensives by the Lebanese army on one front and the Syrian army and Hezbollah on the other.
Part of an agreed exchange went ahead on Thursday as wounded ISIS fighters were swapped for bodies of pro-government forces.
But the fate of the main part of the convoy is uncertain after the coalition said it had seen the buses turning back into Syrian government territory on Thursday.
Syria’s Assad performs Eid prayers near seized ISIS pocket