If you have 2-3 hours to spend in Gateshead, here are some suggestions:
Take a walk across the Gateshead Millennium Bridge, an iconic pedestrian and cyclist bridge spanning the River Tyne. The walk takes around 10-15 minutes each way and offers great views of the Newcastle Quayside.
Visit the BALTIC Centre for Contemporary Art, a modern art museum housed in a converted flour mill. Admission is free and typically takes around 1-2 hours to explore the current exhibitions.
Check out the Gateshead International Stadium, a sports complex that has been host to a number of international and national events. Stadium tours are available and typically take around 1 hour.
These are just a few ideas to get you started - enjoy exploring Gateshead!