The Wellington Monument
The main entrance to the Phoenix Park is at Parkgate Street and after 5 minutes walk you pass by the Wellington Monument. This 62m tall obelisk is actually the tallest obelisk in Europe and was completed in 1861. It was built to commemorate the victories of the 'Iron Duke' Arthur Wellesley Duke of Wellington.
The park contains Dublin Zoo but I was rather attracted by the big sportsgrounds including cricket and polo. As both sports are not very well known in Austria I have no clue how these games are actually played but it was just so amazing to lie in the sun and watch it, especially the poloplayers.