Pray two on entering the masjid
إِذَا دَخَلَ أَحَدُكُمُ الْمَسْجِدَ فَلَا يَجْلِسْ حَتَّى يُصَلِّيَ رَكْعَتَيْنِ
Idha dakhala ahadukumu-l-masjida fa-la yajlis hatta yusalliya rak'atayn.
"When one of you enters the mosque, let him not sit until he has prayed two rakahs."
Narrated by Abu Qatadah. Sahih al-Bukhari 444, Sahih Muslim 714
A short reflection
Tahiyyat al-Masjid. A greeting offered by the body before the mouth speaks. Two rakahs as the cost of entry.