Fans of fresh air will love this place. The park is quite large and also the cruising area does not extend just around the Lion Bridge (Löwenbrücke), but also to on the north to the other bridge which path (Bremer Weg) leads to the statue Siegessäule.
You may find that the Lions bridge is closed, but when you find it you know you're on the right place. We suggest you to take a further walk up to the other bridge (depend from which direction you arrived). Place around that second bridge is also cruising area.
Tiergarten is overcrowded especially during summer months, and is completely amazing during Berlin gay pride (Christopher Street Day - CSD) in June. Mostly around the street Strasse des 17. Juni that cross the whole park. The wood is full and you can see many explicit scenes. Take care to leave the park and nature clean without trash or litter.