1. Drury Street car park
This is definitely one of the safest place to lock a bike around Dublin with space for up to 330 bikes to be locked. The car park is free to use 24 hours a day 7 days per week with cctv covering the floor.
2. Beside the GPO
This area has plenty of footfall coming in and out of Penney's and also has a good Garda presence around the area. The bike racks are large in number so you should find an available one most of the time.
3. Pearse Street Garda Station
Being right next to a Garda station makes this location ideal for cyclists. It's also quite a convenient location being located many of the many areas throughout the city centre.