I never went to 500, so I cannot speak on their gym. I just recall the pool being open to us in 520. I could see the pool from various upper floors in 520, and it looked nice. Resort vibes.

The gym in 520 is very basic and small imo. I sadly never used it for fear of covid cooties, but they did have my favorite old school elliptical. It seemed to get plenty of use, but I never was back there enough to know how crowded it was. I had my own bike for spinning in my apartment and walked and ran the neighborhood. Occasionally rode my bike outside, too.

The nicest gym I have experienced was at 300 Saint Paul, that PMC building. I hate PMC, and I hate that they put the gym nearly at the top of the building and no elevator access, but that gym was amazing. They had like 6 Peloton bikes before Peloton took off during covid, many treadmills, an entire functional fitness area with ropes, traditional strength training stuff, so many free weights, a squat rack... It was great. And all free to residents.

Another building that had a nice gym was 225 N Calvert. It wasn't too large or too small, and it had many more stationary bikes for spinning (including 2 or 3 Peloton bikes), a few studio rooms, many treadmills, squat rack, many free weights, ellipticals, couple rowers, etc.. Free for tenants of course.

There is an Under Armor gym downtown in an old bank I think, but it is a bit of a walk from 520 Park. Closer to 300 Saint Paul. But obviously you have to pay extra/join for that.