public class BasePage
{
    public int Id { get; set; }
    ...
}

public class Region : BasePage
{
    public virtual MapCoordinates Map { get; set; }
    ...
}

public class Place: BasePage
{
    public virtual MapCoordinates Map { get; set; }
    ...
}

public class MapCoordinates
{
    [Key, ForeignKey("BasePage")]
    public int Id { get; set; }

    public virtual BasePage BasePage { get; set; }
    ...
}

public class BasePage
    {
        public int Id { get; set; }

        public virtual MapCoordinate Map { get; set; }
        ...
    }

    public class Region : BasePage
    {
        ...
    }

    public class Place: BasePage
    {
        ...
    }

    public class MapCoordinate
    {
        [Key]
        public int BasePageId { get; set; }
        ...
    }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<BasePage>()
                    .HasRequired(e => e.MapCoordinate)
                    .WithRequiredPrincipal();

        modelBuilder.Entity<BasePage>().ToTable(BasePages);
        modelBuilder.Entity<MapCoordinate>().ToTable(MapCoordinates);
    }