On 30 November 1807, General Junot led 1,200 very tattered and weary French infantry into Lisbon. The rest of the army was far behind as they'd taken an ill-advised route along the Tejo (Tagus) river, the weather was bad and they'd run out of supplies. It's quite possible that they had no dry ammunition. However, the Portuguese Court and senior officials had left for Brazil the previous day, taking with them much of the wealth of the country so there was no one to organise opposition.
On 13 December 1807, Junot paraded 6,000 refreshed and re-equipped men in Rossio Square. A cannonade was sounded and the Portuguese royal standard, flying from the castle of São Jorge, on the nearby hill top, was replaced by the French Tricolour. There was a riot followed by a curfew, confiscation of weapons and other repressive measures.
A panoramic view of Lisbon looking approximately north. This can be panned and zoomed.
The Castle of São Jorge is on the hill to the right of centre.
The Tejo River is on the far right.
Rossio Square is in the valley to the right and behind the tower crane.