This is common with condos because you do not own the land underlying the unit - it belongs to your Homeowner's Association.  You can use the current Fair Market Value (FMV) of your condo for depreciation.  

It is wise to look at a couple of online home sale sites for your current FMV, as the FMV on your property tax bill is likely out of date.  If the current value is different than what is reported on your property tax bill, make sure you print a copy and keep it with your records.