black stripe cutout day flag isolated mourn mourning national national day National day of mourning Poland 17th 17th of march 4 leaf clover Bishop card celebration clover eire four-leaveflover green invitation ireland irish march march17th national celebration national celebration day plant proud shamrock St Patrick's Day St Patricks day symbol lake lucerne Luzerne swiss Swiss National Day switzerland alps cities city river Zurich buda Budapest dark exhibition gallery history light night palace royal banner color colored colors colour coloured colours decoration decorative display distinct distinctive flow government National-Day nationalism Patriotic patriotism pride Singapore symbolic symbolism arch banners decorated decorations Flags four-storeys-high gardens Istana-Park park pools reflecting-pools reflections water