You can see the location of the all three lookout spots on this Map!!
Further information of the each spots, please click the following link.
1. Kasamatsu Park (傘松公園) MUST SEE!
The traditional view of Amanohashidate "bridge to the heaven"
http://seasidekyoto.blogspot.jp/2013/01/look-out-spot-kasamatsu-park.html
2. Amanohashidate Sessyu lookout spot (天橋立雪舟観展望休憩所)
http://seasidekyoto.blogspot.jp/2013/01/viewing-point-in-miyazu.html
3 Ouchi-touge ichiji-kan park (大内峠一字観公園)
***This look out point is also nice although you need a bit effort to reach.