Rivnuts from Homestead, PA on 8/16/2023 6:53:38 PM:
The question of parking in Pittsburgh while riding is a much-travelled question on this forum. Upon searching this forum, you'll find several posts responding to this question.
If proximity to the actual terminus of the GAP Trail in Point State Park in Pittsburgh, you'll find numerous indoor parking garages by Googling "Pittsburgh Parking Garages" or Parkopedia.com. However, these won't be cheap as daily rates are typically $20 a day or more.
There are some less expensive outdoor lots across the rivers from the terminus such as Highmark Stadium that have lower rates and are rideable from downtown via bridge sidewalks.
Free parking is not readily available downtown or is less safe from theft or damage. A couple of free parking options along the trail or its alternate including the South Side Riverfront Park about 3 miles from the terminus or at the Waterfront Shopping Center in Homestead about 10 miles from the terminus. Both have ample parking area and a fair amount of daytime pedestrian traffic for some level of security. Given you'll be gone several days, I believe the Waterfront Shopping Center would be better as it has a number of major stores therein with lighting in their parking areas,
Other Pittsburgh locals may have some other thoughts.