AER Building is a shopping mall + hotel located about 5 minutes walk from the Sendai Station. The 31st floor of AER is an open observation deck, where you can see the entire Sendai downtown area.
Downtown Sendai from the AER Observation Deck
From here you can see the biggest shopping area, Ichibancho Shopping Arcade ( looks like a very long tunnel between buildings. I go there almost every two days…)