All of them are about 5-10 minutes walking distance apart and about 4-8 min walking from Old Town. Central is nothing to write home about and not very classy, but in a quiet spot and some of their more expensive rooms have big balconies. Olympia was once highest building on Tallinn (it was built for Olympics back in 1980) and has still certain charm, while Blue City Center has nice lounge (and open terrace) with unbeatable views on the highest floor.