Two grand San Antonio institutions — Mission 4 Drive-In and the late Linda Pace — will unite a congregation this Thursday to celebrate and mourn them on the anniversary of Pace’s birthday. The venerable outdoor theater, now fallen into disrepair and soon to be demolished by the city (though, somewhat thankfully, to make way for a new public library), will screen one final film before being silenced forever: Edgar Arcenaux’s eight-minute Old Man Hill, which was purchased from the artist after his 2006 Artpace residency by Artpace founder Linda Pace herself. Arcenaux, whose grandfather was Bosnian, filmed the documentary in 1995 after a massacre of Bosnian Muslims, recording the subsequent war-torn landscape and architectural diaster. “Old Man Hill is a memorial to that which cannot be represented,” Arceneaux has said. The film will screen only at this event, and never again, and its screening will be accompanied by release of silver balloons spelling “Old Man Hill,” his grandfather’s nickname, in Bosnian. “`The film` reveals meaning to us as it disappears from our perception,” says the artist. Much like the redoubtable, still-shining Ms. Pace, and the eminent, now-shabby Mission 4 Drive-In Theatre itself. Free, 7-9pm Thursday, 3100 Roosevelt.