If you come to MM21, the Land Mark Tower must be in your sight. It's Japan's tallest building, 296 meter. This building has shopping malls(B2-5F), restaurants(B2-5F), Hotel(49F-70F) and offices. I highly recomend you to visit "sky garden" which is located 69F in this building. You can see 360��view from 273 meter!! But it's not free. The fee is as follows.
Adult:1,000 yen
Adult(over 65):800 yen
High school:800 yen
child:500 yen
Infant(over 4) :200 yen
The other recommendation is hotel which name is Royal Park Hotel(the guest room is located 47F-67F). You can see great view from your rooom!! If you will stay this hotel, I hope the weather will be fine!! You can' t see outside because of fog or cloud if the weather is bad...